I always assumed that when I won the Publisher's Clearing House sweepstakes, or maybe a celebrity golf tournament, and got my GIANT CHECK, I'd have to sit around and wait for the real, regular-sized check before I got the money. 

Turns out that's NOT TRUE.  According to Mental Floss you actually CAN deposit a giant novelty check, as long as it has all the key info on it.

ANYTHING can be a valid check as long as it has the payer's name and account number, the name and location of their bank, the date, the words "pay to the order of," the payee's name, the dollar amount, and the signature.

In other words . . . as long as everything on the giant check is the same as it would be on a regular check, it's legit.  That's why you can order your new checks from random companies and not your bank . . . anyone can make valid checks for you.

This doesn't just go for giant checks either.  In theory, you could write someone a check on a napkin or a Post-It note, and even though it might take a few phone calls, it SHOULD be accepted.