Q: What do you call Santa's little helpers?

Q: What do you call Santa's little helpers?
A: Subordinate clauses!

This is a language-based pun. People that know that such a thing as a subordinate clause exist are more likely to find this funny, so be sure to tell it in your English class.

A subordinate clause is a part of a sentence that is found after a subordinate conjunction that cannot stand on its own 😉.

Anyone helping Santa would be subordinate to him, and sometimes fake Santa causes are called Santa's helpers, so to call them subordinate clauses does make sense.

That being said, the pun would be stronger if the Santa's helper was both subordinate to Santa, and also unable to stand on its own. I don't think that it would improve the joke, but if you changed it to "What do you call a legless guy dressed up in a saint nick costume? A subordinate clause" the pun would be better.

Anyway - I sort of like this one.