Similar to a catch 22. It is
used for the rare occasion when you
run into a catch 22, because you in
fact are not 21.
Friend: Why didn't you come to Vegas with
us?
Me:
Well, I have my court date for underaged drinking and I'm not 21 so I wouldn't be able to do anything in Vegas.
Friend: Man that is a catch 22
Me: More
like a catch 21!