Maybe it has some magical power in the toon world that allows it to regain its shape, like a special spell or a fairy's touch.
Well, in toon stories, the rules of physics often don't apply in the same way as in the real world. The flattened wolf might pop back into shape due to the will of the storyteller or the comical nature of the toon universe. It could be that the other characters in the story do something to help it, like pour a magic potion on it or use a special device. Or perhaps it's just part of the wacky and unpredictable nature of the toon world where things can happen for no logical reason other than to create a humorous or exciting moment in the story.
In the toon story, it could be that the wolf's elasticity is a special trait. When the flattening force is removed, it naturally springs back into shape, just like a deflated balloon that is reinflated and resumes its original form. Also, there might be some comical mechanism involved, such as the wolf eating a special item that causes it to puff back up.