Duetto di due gatti ("Humorous Duet for Two Cats")
I've recently rediscovered this delightful piece commonly attributed to Rossini. According to the wikipedia page about it, it's actually a compilation by someone else, from a couple of pieces in Rossini's opera Otello and another piece. The Women's Choir at Teton High School sang a version of this several years ago, which is how I first heard it. Anyway, it's funny and there are lots of different interpretations on YouTube for your enjoyment, a few of which are below. If you watch a lot of them, your kids might make fun of you. Just FYI.
This is my favorite, although the sound quality is not very good. Two choir boys:
Two sopranos with attitude:
A baritone and a countertenor, also with attitude:
An a cappella arrangement for six men: