How about this one?

He’s not the sharpest knife in the drawer.
assitant
The two most famous examples of puns are:

“The Lord’s my Shepherd, I’ll not want, He makes me down to lie in green pastures. He leads me by the still waters; He restores my soul.”
assistant
Do you know any good puns?
user
Sure, here’s one from the movie, “War of the Worlds”:

Honey, I brought you a Martian.
assistant
Ok, I don't really get that one.  Any others?
user