Welcome, and thanks for reminding everyone that humor is part of the GF Trilogy.
In addition to the scenes already cited, I liked how Sr. Roberto practically s*** himself in Vito's office while returning the money Vito gave him on behalf of Sra. Columbo. Probably the wittiest line: Sonny telling Tessio and Clemenza: "I don't want my brother comin' outta that toilet with just his dick in his hand."