For my 3 year old son's birthday he wanted a fishing party.  We set up a "pond" (big washtub) full of small rubber duckies, frogs, fish, etc. and gave the kids fish nets to scoop with. At the same time we had a magnet fishing game going (used a big blue sheet for the lake and a long flat cardboard box for the pier).  Then we had "turtle races" (cut out turtles of tagboard and threaded them on 6 foot pieces of string tied to bricks at the other end--kids wiggle string to get turtles to race). Then it was lunchtime--"frogs on lily pads"--green cream cheese on mini bagels with a Gumi frog and "fishing poles"--pretzel logs dipped in peanut butter 'bait' used to catch goldfish crackers.  We also used fish shaped cookie cutters to cut out cheese and turkey slices and served a fruit salad and juice. The cake was a fish shaped sheet cake that I made by trimming the middle into an oval and making fins and a tail out of what I cut off.  I frosted it all pink and used mini marshmallows to make scales. The highlight of the party came after lunch. We gave each kid a "tackle box" (made from an egg carton spray painted orange with a handle attached) and the fishing rod from the magnet fishing game which we had tied onto a great big fish made out of two sheets of wrapping paper hot glued together--kind of like a piñata. The kids "reeled in" the big fish together which ripped the paper open and lots of goodies fell out--12 different things for each kid so they could fill up each slot of their tackle box (really cheap things like rubber fish and bugs, magnifying glasses, mini playdough, and squirt frogs).  It was a really fun party and cheap too--for 5 kids we spent less than $50 (plus food). We made the "piñata" and decorated with paper plate fish and crepe paper streamers.