My BF was (a very creepy, not so cute and cuddly) Elmo last year, LOL. Who's 38 and fits into a 3T Elmo costume? HE DOES! I love the Elmo/Katy Perry idea, super cute.
Have you seen the 'shake weight' parody on SNL? Yeah... that's what I'm going as this year, LOL!!
Some of our friends a few years ago dressed as a protologist and patient... she was the 'dirty doctor' and he simply wore a hospital gown with a big fake plastic butt hanging out the back... the pictures were HILARIOUS.
As far as the foursome, any movie with 4 people would be funny! Ninja Turtles (they make really cute womens costumes), Larry, Curly, Moe, and Shep... or if you want to stick with you and your hubby, check out www.3wishes.com ... it's adult, but they've got some cute his and hers ideas ;) HAVE FUN!!