I'm not sure if this is from "Goof On The Roof", but I also like the bit where the boys are working in someone's house and Shemp starts to paint around a radio. Which leads to the following:
Moe, (to Shemp),..."Hey, Imbecile !!! MOVE the radio."
Shemp,................."OH!! Move it."
Larry, (to Moe ),....."Stupid, ain't he?"
Moe, (to Larry),...."Look who's talking."
Just cracks me up every time.