a party fit for a four-year-old...

It's been a couple of years since we've put on a 'friend party' for one our kids' birthdays.  I realized some time ago that since a three-year-old very clearly understands the concept of a birthday party, there was no way we were going to get through the big day this year without friends, decorations, party favors, games, and a pinata...all party necessities.  Also a necessity in this case?  That all of the above incorporate lots of Little Mermaid.