Pussywillow Hollow is a swampy region adjoining the Smurf Forest that appears in the Smurfs cartoon show. It is separated by a mist on the other side of Toad River. It serves as home for both the Pussywillow Pixies and the Wartmongers.
In the EMPATH: The Luckiest Smurf story series, the region itself is actually an alternate dimension, and the fog separating it from the Smurf Forest is simply a dimensional gateway between that dimension and the real world.