diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index 837bd47b0d95..0d1d71d7c7d0 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/py-polars/polars/dataframe/frame.py
@@ -6992,7 +6992,7 @@ def get_column(self, name: str) -> Series:
 
     def fill_null(
         self,
-        value: Any | None = None,
+        value: Any | Expr | None = None,
         strategy: FillNullStrategy | None = None,
         limit: int | None = None,
         *,
@@ -7103,7 +7103,7 @@ def fill_nan(self, value: Expr | int | float | None) -> DataFrame:
 
         Warnings
         --------
-        Note that floating point NaNs (Not a Number) are not missing values!
+        Note that floating point NaNs (Not a Number) are not missing values.
         To replace missing values, use :func:`fill_null`.
 
         See Also
diff --git a/py-polars/polars/expr/expr.py b/py-polars/polars/expr/expr.py
index cd3cc21c8f77..b393b220debf 100644
--- a/py-polars/polars/expr/expr.py
+++ b/py-polars/polars/expr/expr.py
@@ -2832,6 +2832,11 @@ def shift(
         This method is similar to the `LAG` operation in SQL when the value for `n`
         is positive. With a negative value for `n`, it is similar to `LEAD`.
 
+        See Also
+        --------
+        backward_fill
+        forward_fill
+
         Examples
         --------
         By default, values are shifted forward by one index.
@@ -2887,7 +2892,7 @@ def shift(
 
     def fill_null(
         self,
-        value: Any | None = None,
+        value: Any | Expr | None = None,
         strategy: FillNullStrategy | None = None,
         limit: int | None = None,
     ) -> Self:
@@ -2907,6 +2912,10 @@ def fill_null(
             Number of consecutive null values to fill when using the 'forward' or
             'backward' strategy.
 
+        See Also
+        --------
+        fill_nan
+
         Examples
         --------
         >>> df = pl.DataFrame(
@@ -2993,6 +3002,20 @@ def fill_nan(self, value: int | float | Expr | None) -> Self:
         """
         Fill floating point NaN value with a fill value.
 
+        Parameters
+        ----------
+        value
+            Value used to fill NaN values.
+
+        Warnings
+        --------
+        Note that floating point NaNs (Not a Number) are not missing values.
+        To replace missing values, use :func:`fill_null`.
+
+        See Also
+        --------
+        fill_null
+
         Examples
         --------
         >>> df = pl.DataFrame(
@@ -3025,6 +3048,11 @@ def forward_fill(self, limit: int | None = None) -> Self:
         limit
             The number of consecutive null values to forward fill.
 
+        See Also
+        --------
+        backward_fill
+        shift
+
         Examples
         --------
         >>> df = pl.DataFrame(
@@ -3056,6 +3084,11 @@ def backward_fill(self, limit: int | None = None) -> Self:
         limit
             The number of consecutive null values to backward fill.
 
+        See Also
+        --------
+        forward_fill
+        shift
+
         Examples
         --------
         >>> df = pl.DataFrame(
diff --git a/py-polars/polars/lazyframe/frame.py b/py-polars/polars/lazyframe/frame.py
index d0ee96efdc65..4e4effa58bff 100644
--- a/py-polars/polars/lazyframe/frame.py
+++ b/py-polars/polars/lazyframe/frame.py
@@ -4909,7 +4909,7 @@ def gather_every(self, n: int, offset: int = 0) -> Self:
 
     def fill_null(
         self,
-        value: Any | None = None,
+        value: Any | Expr | None = None,
         strategy: FillNullStrategy | None = None,
         limit: int | None = None,
         *,
@@ -4930,6 +4930,10 @@ def fill_null(
         matches_supertype
             Fill all matching supertypes of the fill `value` literal.
 
+        See Also
+        --------
+        fill_nan
+
         Examples
         --------
         >>> lf = pl.LazyFrame(
@@ -5046,8 +5050,12 @@ def fill_nan(self, value: int | float | Expr | None) -> Self:
 
         Warnings
         --------
-        Note that floating point NaN (Not a Number) are not missing values!
-        To replace missing values, use :func:`fill_null` instead.
+        Note that floating point NaNs (Not a Number) are not missing values.
+        To replace missing values, use :func:`fill_null`.
+
+        See Also
+        --------
+        fill_null
 
         Examples
         --------
diff --git a/py-polars/polars/series/series.py b/py-polars/polars/series/series.py
index 1d8892e08ee2..df9b9c4f63c9 100644
--- a/py-polars/polars/series/series.py
+++ b/py-polars/polars/series/series.py
@@ -4843,6 +4843,15 @@ def fill_nan(self, value: int | float | Expr | None) -> Series:
         value
             Value used to fill NaN values.
 
+        Warnings
+        --------
+        Note that floating point NaNs (Not a Number) are not missing values.
+        To replace missing values, use :func:`fill_null`.
+
+        See Also
+        --------
+        fill_null
+
         Examples
         --------
         >>> s = pl.Series("a", [1, 2, 3, float("nan")])
@@ -4859,7 +4868,7 @@ def fill_nan(self, value: int | float | Expr | None) -> Series:
 
     def fill_null(
         self,
-        value: Any | None = None,
+        value: Any | Expr | None = None,
         strategy: FillNullStrategy | None = None,
         limit: int | None = None,
     ) -> Series:
@@ -4876,6 +4885,10 @@ def fill_null(
             Number of consecutive null values to fill when using the 'forward' or
             'backward' strategy.
 
+        See Also
+        --------
+        fill_nan
+
         Examples
         --------
         >>> s = pl.Series("a", [1, 2, 3, None])