The end of "Stan's Old Owner" when Stan realizes his old owner was more of an evil scientist than he let on. Stan tell him to come close so he can whisper to him the secret of how he can talk. Then, once he is within Stan's reach, Stan gives him a stiff jab.
Another one from the same episode, Stan gives a brief bio on a new character and here's what he says about Ian:
Stan: Dr. Ian Calloway, AHHHHHHH!
In "Too Short", when the kids are at school Stan makes sculptures of them out of cheese to keep him company, then eats them questioning why he made them out of cheese.
From "Freaky Fido"
Stan: I'm gonna need an agent, sunglasses, and a political cause I don't really understand.