diff --git a/pandas/core/arrays/_mixins.py b/pandas/core/arrays/_mixins.py
index 2976747d66dfa..4e96685ba77df 100644
--- a/pandas/core/arrays/_mixins.py
+++ b/pandas/core/arrays/_mixins.py
@@ -17,7 +17,9 @@ class NDArrayBackedExtensionArray(ExtensionArray):
     ExtensionArray that is backed by a single NumPy ndarray.
     """
 
-    _ndarray: np.ndarray
+    @property
+    def _ndarray(self) -> np.ndarray:
+        raise AbstractMethodError(self)
 
     def _from_backing_data(self: _T, arr: np.ndarray) -> _T:
         """
diff --git a/pandas/core/arrays/numpy_.py b/pandas/core/arrays/numpy_.py
index 23a4a70734c81..c999e8caf2d9a 100644
--- a/pandas/core/arrays/numpy_.py
+++ b/pandas/core/arrays/numpy_.py
@@ -153,7 +153,6 @@ class PandasArray(
     # pandas internals, which turns off things like block consolidation.
     _typ = "npy_extension"
     __array_priority__ = 1000
-    _ndarray: np.ndarray
 
     # ------------------------------------------------------------------------
     # Constructors
@@ -172,9 +171,13 @@ def __init__(self, values: Union[np.ndarray, "PandasArray"], copy: bool = False)
         if copy:
             values = values.copy()
 
-        self._ndarray = values
+        self._data = values
         self._dtype = PandasDtype(values.dtype)
 
+    @property
+    def _ndarray(self) -> np.ndarray:
+        return self._data
+
     @classmethod
     def _from_sequence(cls, scalars, dtype=None, copy: bool = False) -> "PandasArray":
         if isinstance(dtype, PandasDtype):
diff --git a/pandas/core/tools/datetimes.py b/pandas/core/tools/datetimes.py
index 8fcc5f74ea897..929fd0dc334c8 100644
--- a/pandas/core/tools/datetimes.py
+++ b/pandas/core/tools/datetimes.py
@@ -550,7 +550,8 @@ def _adjust_to_origin(arg, origin, unit):
 
 
 @overload
-def to_datetime(
+# error: Overloaded function signatures 1 and 3 overlap with incompatible return types
+def to_datetime(  # type: ignore[misc]
     arg: DatetimeScalar,
     errors: str = ...,
     dayfirst: bool = ...,
@@ -567,7 +568,8 @@ def to_datetime(
 
 
 @overload
-def to_datetime(
+# error: Overloaded function signatures 2 and 3 overlap with incompatible return types
+def to_datetime(  # type: ignore[misc]
     arg: "Series",
     errors: str = ...,
     dayfirst: bool = ...,
@@ -585,7 +587,7 @@ def to_datetime(
 
 @overload
 def to_datetime(
-    arg: Union[List, Tuple],
+    arg: Union[List, Tuple, ArrayLike],
     errors: str = ...,
     dayfirst: bool = ...,
     yearfirst: bool = ...,
diff --git a/pandas/plotting/_matplotlib/tools.py b/pandas/plotting/_matplotlib/tools.py
index 98aaab6838fba..71b708b6520d8 100644
--- a/pandas/plotting/_matplotlib/tools.py
+++ b/pandas/plotting/_matplotlib/tools.py
@@ -351,7 +351,7 @@ def handle_shared_axes(
                     _remove_labels_from_axis(ax.yaxis)
 
 
-def flatten_axes(axes: Union["Axes", Sequence["Axes"]]) -> Sequence["Axes"]:
+def flatten_axes(axes: Union["Axes", Sequence["Axes"]]) -> np.ndarray:
     if not is_list_like(axes):
         return np.array([axes])
     elif isinstance(axes, (np.ndarray, ABCIndexClass)):