On the spelling of drinking vessels

[As heard by Dad]
Theo: I want to see you pee [garbled].
Dad: What!? You want to see me pee?
Theo: I want the see you pee cup!
Mom: [Fits of laughter]
Dad: [Between spasms] Oh...the C-U-P cup...

The C-U-P cup was given to Theo by a daycare provider when he learned to spell "cup". It is a favorite of both the children, but I had never been caught off-guard until now. This conversation mirrors a (practical) joke that was told to me in first grade.

Antagonist: Spell iCup.
Me: I-C-U-P.
Antagonist: Stop looking at me while I'm peeing. That's gross.

And here 22 years later, I fell for it again. It was much funnier the second time around.