Just thought of a couple more:

Trio or quartet (male and female) sing in close harmony: "Call Roto-Rooter, that's the name."
Bass solo: "And away goes trouble, down the drain."

One of Philadelphia's radio commercials has endured past the death of the "singer". The elderly man advertised his basement-waterproofing business by singing part of the bridge from "Sweet Lorraine" (somewhat tunelessly and lispingly, with no accompaniment): "When it's raining, I don't miss the sun, 'cause it's in my baby's smile." He's gone now, but his family still runs the business... and the recording of that man singing that song in their commercials! It's awful-ly sweet of them.