A very early one was his appearance on the Carol Burnett show, when he starred as a strange man attempting to console Carol as a grieving widow at a funeral. After taping the sketch, Robin asked Carol if they could do it again, and the result was even funnier.
[Original line, to mourners waiting to talk to Carol] I wouldn't wait, I'm gonna be here a while.
[Ad-libbed version, same part] I wouldn't wait, I'm gonna be here a while. There's some coffee in the embalming room, but it tastes funny, be careful.