diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 7be06fe92c418..25939bcdc7c6a 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -1732,8 +1732,8 @@ def _round(self, freq, mode, ambiguous, nonexistent):
         values = self.view("i8")
         values = cast(np.ndarray, values)
         nanos = to_offset(freq).nanos
-        result = round_nsint64(values, mode, nanos)
-        result = self._maybe_mask_results(result, fill_value=iNaT)
+        result_i8 = round_nsint64(values, mode, nanos)
+        result = self._maybe_mask_results(result_i8, fill_value=iNaT)
         result = result.view(self._ndarray.dtype)
         return self._simple_new(result, dtype=self.dtype)
 
diff --git a/pandas/core/arrays/integer.py b/pandas/core/arrays/integer.py
index ae44acf06591f..3f5c550545aad 100644
--- a/pandas/core/arrays/integer.py
+++ b/pandas/core/arrays/integer.py
@@ -371,14 +371,14 @@ def astype(self, dtype, copy: bool = True) -> ArrayLike:
         if isinstance(dtype, ExtensionDtype):
             return super().astype(dtype, copy=copy)
 
+        na_value: float | np.datetime64 | lib.NoDefault
+
         # coerce
         if is_float_dtype(dtype):
             # In astype, we consider dtype=float to also mean na_value=np.nan
             na_value = np.nan
         elif is_datetime64_dtype(dtype):
-            # error: Incompatible types in assignment (expression has type
-            # "datetime64", variable has type "float")
-            na_value = np.datetime64("NaT")  # type: ignore[assignment]
+            na_value = np.datetime64("NaT")
         else:
             na_value = lib.no_default
 
diff --git a/pandas/core/construction.py b/pandas/core/construction.py
index b5a17e1ef882e..98dfad72142f6 100644
--- a/pandas/core/construction.py
+++ b/pandas/core/construction.py
@@ -52,10 +52,10 @@
     is_integer_dtype,
     is_list_like,
     is_object_dtype,
-    is_sparse,
     is_string_dtype,
     is_timedelta64_ns_dtype,
 )
+from pandas.core.dtypes.dtypes import DatetimeTZDtype
 from pandas.core.dtypes.generic import (
     ABCExtensionArray,
     ABCIndex,
@@ -549,12 +549,10 @@ def sanitize_array(
 
     subarr = _sanitize_ndim(subarr, data, dtype, index)
 
-    if not (is_extension_array_dtype(subarr.dtype) or is_extension_array_dtype(dtype)):
-        # error: Argument 1 to "_sanitize_str_dtypes" has incompatible type
-        # "ExtensionArray"; expected "ndarray"
-        subarr = _sanitize_str_dtypes(
-            subarr, data, dtype, copy  # type: ignore[arg-type]
-        )
+    if not (
+        isinstance(subarr.dtype, ExtensionDtype) or isinstance(dtype, ExtensionDtype)
+    ):
+        subarr = _sanitize_str_dtypes(subarr, data, dtype, copy)
 
         is_object_or_str_dtype = is_object_dtype(dtype) or is_string_dtype(dtype)
         if is_object_dtype(subarr.dtype) and not is_object_or_str_dtype:
@@ -599,7 +597,7 @@ def _sanitize_ndim(
 
 
 def _sanitize_str_dtypes(
-    result: np.ndarray, data, dtype: Optional[DtypeObj], copy: bool
+    result: np.ndarray, data, dtype: Optional[np.dtype], copy: bool
 ) -> np.ndarray:
     """
     Ensure we have a dtype that is supported by pandas.
@@ -613,11 +611,7 @@ def _sanitize_str_dtypes(
         # GH#19853: If data is a scalar, result has already the result
         if not lib.is_scalar(data):
             if not np.all(isna(data)):
-                # error: Argument "dtype" to "array" has incompatible type
-                # "Union[dtype[Any], ExtensionDtype, None]"; expected "Union[dtype[Any],
-                # None, type, _SupportsDType, str, Union[Tuple[Any, int], Tuple[Any,
-                # Union[int, Sequence[int]]], List[Any], _DTypeDict, Tuple[Any, Any]]]"
-                data = np.array(data, dtype=dtype, copy=False)  # type: ignore[arg-type]
+                data = np.array(data, dtype=dtype, copy=False)
             result = np.array(data, dtype=object, copy=copy)
     return result
 
@@ -666,7 +660,7 @@ def _try_cast(
     ):
         return arr
 
-    if isinstance(dtype, ExtensionDtype) and (dtype.kind != "M" or is_sparse(dtype)):
+    if isinstance(dtype, ExtensionDtype) and not isinstance(dtype, DatetimeTZDtype):
         # create an extension array from its dtype
         # DatetimeTZ case needs to go through maybe_cast_to_datetime but
         # SparseDtype does not
diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 3f3d9f9f2833b..a3744ffa7f9bc 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -1400,11 +1400,13 @@ def soft_convert_objects(
         # GH 20380, when datetime is beyond year 2262, hence outside
         # bound of nanosecond-resolution 64-bit integers.
         try:
-            values = lib.maybe_convert_objects(
+            converted = lib.maybe_convert_objects(
                 values, convert_datetime=datetime, convert_timedelta=timedelta
             )
         except (OutOfBoundsDatetime, ValueError):
             return values
+        if converted is not values:
+            return converted
 
     if numeric and is_object_dtype(values.dtype):
         converted = lib.maybe_convert_numeric(values, set(), coerce_numeric=True)
@@ -1446,10 +1448,9 @@ def convert_dtypes(
     dtype
         new dtype
     """
-    is_extension = is_extension_array_dtype(input_array.dtype)
     if (
         convert_string or convert_integer or convert_boolean or convert_floating
-    ) and not is_extension:
+    ) and isinstance(input_array, np.ndarray):
         inferred_dtype = lib.infer_dtype(input_array)
 
         if not convert_string and is_string_dtype(inferred_dtype):
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 484b01f2c04f0..d1d1993931062 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -3300,14 +3300,10 @@ def transpose(self, *args, copy: bool = False) -> DataFrame:
             )
 
         else:
-            # error: Incompatible types in assignment (expression has type
-            # "ndarray", variable has type "List[Any]")
-            new_values = self.values.T  # type: ignore[assignment]
+            new_arr = self.values.T
             if copy:
-                new_values = new_values.copy()
-            result = self._constructor(
-                new_values, index=self.columns, columns=self.index
-            )
+                new_arr = new_arr.copy()
+            result = self._constructor(new_arr, index=self.columns, columns=self.index)
 
         return result.__finalize__(self, method="transpose")
 
@@ -3682,17 +3678,15 @@ def _set_item_frame_value(self, key, value: DataFrame) -> None:
                     value = value.reindex(cols, axis=1)
 
         # now align rows
+        arraylike = _reindex_for_setitem(value, self.index)
+        self._set_item_mgr(key, arraylike)
 
-        # error: Incompatible types in assignment (expression has type "ExtensionArray",
-        # variable has type "DataFrame")
-        value = _reindex_for_setitem(value, self.index)  # type: ignore[assignment]
-        self._set_item_mgr(key, value)
-
-    def _iset_item_mgr(self, loc: int, value) -> None:
+    def _iset_item_mgr(self, loc: int | slice | np.ndarray, value) -> None:
+        # when called from _set_item_mgr loc can be anything returned from get_loc
         self._mgr.iset(loc, value)
         self._clear_item_cache()
 
-    def _set_item_mgr(self, key, value):
+    def _set_item_mgr(self, key, value: ArrayLike) -> None:
         try:
             loc = self._info_axis.get_loc(key)
         except KeyError:
@@ -3707,9 +3701,9 @@ def _set_item_mgr(self, key, value):
         if len(self):
             self._check_setitem_copy()
 
-    def _iset_item(self, loc: int, value):
-        value = self._sanitize_column(value)
-        self._iset_item_mgr(loc, value)
+    def _iset_item(self, loc: int, value) -> None:
+        arraylike = self._sanitize_column(value)
+        self._iset_item_mgr(loc, arraylike)
 
         # check if we are modifying a copy
         # try to set first as we want an invalid
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 6b4e3c7caef50..25c10c215e8cc 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -3541,7 +3541,8 @@ def _maybe_cache_changed(self, item, value) -> None:
         The object has called back to us saying maybe it has changed.
         """
         loc = self._info_axis.get_loc(item)
-        self._mgr.iset(loc, value)
+        arraylike = value._values
+        self._mgr.iset(loc, arraylike)
 
     @final
     @property
diff --git a/pandas/core/internals/array_manager.py b/pandas/core/internals/array_manager.py
index 294d1fd078b08..d432b7ef443cc 100644
--- a/pandas/core/internals/array_manager.py
+++ b/pandas/core/internals/array_manager.py
@@ -850,7 +850,7 @@ def idelete(self, indexer):
         self._axes = [self._axes[0], self._axes[1][to_keep]]
         return self
 
-    def iset(self, loc: Union[int, slice, np.ndarray], value):
+    def iset(self, loc: Union[int, slice, np.ndarray], value: ArrayLike):
         """
         Set new column(s).
 
@@ -861,12 +861,10 @@ def iset(self, loc: Union[int, slice, np.ndarray], value):
         ----------
         loc : integer, slice or boolean mask
             Positional location (already bounds checked)
-        value : array-like
+        value : np.ndarray or ExtensionArray
         """
         # single column -> single integer index
         if lib.is_integer(loc):
-            # TODO the extract array should in theory not be needed?
-            value = extract_array(value, extract_numpy=True)
 
             # TODO can we avoid needing to unpack this here? That means converting
             # DataFrame into 1D array when loc is an integer
@@ -904,7 +902,10 @@ def iset(self, loc: Union[int, slice, np.ndarray], value):
         assert value.shape[0] == len(self._axes[0])
 
         for value_idx, mgr_idx in enumerate(indices):
-            value_arr = value[:, value_idx]
+            # error: Invalid index type "Tuple[slice, int]" for
+            # "Union[ExtensionArray, ndarray]"; expected type
+            # "Union[int, slice, ndarray]"
+            value_arr = value[:, value_idx]  # type: ignore[index]
             self.arrays[mgr_idx] = value_arr
         return
 
diff --git a/pandas/core/internals/construction.py b/pandas/core/internals/construction.py
index 5b4b710838ef8..6364816b9ab2d 100644
--- a/pandas/core/internals/construction.py
+++ b/pandas/core/internals/construction.py
@@ -843,8 +843,8 @@ def _list_of_dict_to_arrays(
     if columns is None:
         gen = (list(x.keys()) for x in data)
         sort = not any(isinstance(d, dict) for d in data)
-        columns = lib.fast_unique_multiple_list_gen(gen, sort=sort)
-        columns = ensure_index(columns)
+        pre_cols = lib.fast_unique_multiple_list_gen(gen, sort=sort)
+        columns = ensure_index(pre_cols)
 
     # assure that they are of the base dict class and not of derived
     # classes
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index b688f1b4fea5f..549d4337dcf54 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -1062,7 +1062,7 @@ def idelete(self, indexer) -> BlockManager:
         axes = [new_columns, self.axes[1]]
         return type(self)._simple_new(tuple(nbs), axes)
 
-    def iset(self, loc: Union[int, slice, np.ndarray], value):
+    def iset(self, loc: Union[int, slice, np.ndarray], value: ArrayLike):
         """
         Set new item in-place. Does not consolidate. Adds new Block if not
         contained in the current set of items
@@ -1073,6 +1073,7 @@ def iset(self, loc: Union[int, slice, np.ndarray], value):
         if self._blklocs is None and self.ndim > 1:
             self._rebuild_blknos_and_blklocs()
 
+        # Note: we exclude DTA/TDA here
         value_is_extension_type = is_extension_array_dtype(value)
 
         # categorical/sparse/datetimetz
@@ -1429,7 +1430,7 @@ def _slice_take_blocks_ax0(
 
         return blocks
 
-    def _make_na_block(self, placement, fill_value=None):
+    def _make_na_block(self, placement: BlockPlacement, fill_value=None) -> Block:
 
         if fill_value is None:
             fill_value = np.nan
diff --git a/pandas/core/missing.py b/pandas/core/missing.py
index 21c79588317df..2fd39588a3da6 100644
--- a/pandas/core/missing.py
+++ b/pandas/core/missing.py
@@ -888,7 +888,7 @@ def clean_reindex_fill_method(method):
     return clean_fill_method(method, allow_nearest=True)
 
 
-def _interp_limit(invalid, fw_limit, bw_limit):
+def _interp_limit(invalid: np.ndarray, fw_limit, bw_limit):
     """
     Get indexers of values that won't be filled
     because they exceed the limits.
diff --git a/pandas/core/strings/object_array.py b/pandas/core/strings/object_array.py
index edf32bade0657..45f1faa637b85 100644
--- a/pandas/core/strings/object_array.py
+++ b/pandas/core/strings/object_array.py
@@ -56,21 +56,17 @@ def _str_map(self, f, na_value=None, dtype: Optional[Dtype] = None):
         dtype : Dtype, optional
             The dtype of the result array.
         """
-        arr = self
         if dtype is None:
             dtype = np.dtype("object")
         if na_value is None:
             na_value = self._str_na_value
 
-        if not len(arr):
+        if not len(self):
             # error: Argument 1 to "ndarray" has incompatible type "int";
             # expected "Sequence[int]"
             return np.ndarray(0, dtype=dtype)  # type: ignore[arg-type]
 
-        if not isinstance(arr, np.ndarray):
-            # error: Incompatible types in assignment (expression has type "ndarray",
-            # variable has type "ObjectStringArrayMixin")
-            arr = np.asarray(arr, dtype=object)  # type: ignore[assignment]
+        arr = np.asarray(self, dtype=object)
         mask = isna(arr)
         convert = not np.all(mask)
         try:
diff --git a/pandas/tests/extension/test_numpy.py b/pandas/tests/extension/test_numpy.py
index e11e74f16030c..35e5abe9ce4e7 100644
--- a/pandas/tests/extension/test_numpy.py
+++ b/pandas/tests/extension/test_numpy.py
@@ -330,17 +330,6 @@ def test_fillna_frame(self, data_missing):
         # Non-scalar "scalar" values.
         super().test_fillna_frame(data_missing)
 
-    def test_fillna_fill_other(self, data_missing):
-        # Same as the parent class test, but with PandasDtype for expected["B"]
-        #  instead of equivalent numpy dtype
-        data = data_missing
-        result = pd.DataFrame({"A": data, "B": [np.nan] * len(data)}).fillna({"B": 0.0})
-
-        expected = pd.DataFrame({"A": data, "B": [0.0] * len(result)})
-        expected["B"] = expected["B"].astype(PandasDtype(expected["B"].dtype))
-
-        self.assert_frame_equal(result, expected)
-
 
 class TestReshaping(BaseNumPyTests, base.BaseReshapingTests):
     @pytest.mark.skip(reason="Incorrect expected.")