Q: What do you call Santa’s helpers?
A: Subordinate Clauses!

Explanation: Merry Christmas!

In the telling of the story of Santa Claus, the people who help Santa make the toys are typically called elves (one elf, two elves).  They are the helpers; they are not the main attraction.  They are subordinate.

The word subordinate means lower in rank or position, perhaps less important, like the elves when compared to Santa.  This is also true in English grammar when there is a main clause and a subordinate clause.  A subordinate clause is part of a sentence, but it does not have enough meaning by itself.  If I say “When I get home,” there is an obvious question: What will happen when you get home?  That phrase needs more information so we call it subordinate.

This joke is funny (at least to English teachers) because Santa’s helpers are usually known as elves, not as subordinate clauses.

Here is Michael Bublé reading A Visit From St. Nicholas.