Walter Wolf is Slappy Squirrel's arch-enemy who often appeared with her in the fictious Looney Tunes cartoons. He is the most prominent antagonist in the Slappy Squirrel segment, often trying to defeat Slappy by suing her (...And Justice for Slappy) or faking his death to do a sneak attack at Slappy (Hurray For Slappy), but he always fails in his plans. Sometimes, he teams up with Slappy's other long-time foes, like Sid the Squid and Beanie the Brain-Dead Bison. He was voiced by Frank Welker in his first appearance and Jess Harnell in all subsequent appearances. Both actors gave Walter a Yiddish accent.

In the comics, it was revealed he was the star of a TV show that only lasted for 8 episodes, with Slappy Squirrel as his sidekick.