Dd will be one March 2, which seems to be looming really close these days *snif*
When she was in utero our nickname for her was "Melonhead" (there's a story behind this, but if vaginal self-exams squick anybody it'll be tmi for them :LOL) Anyway, we're planning a melon-themed party, with a "watermelon" cake, dark pink & green balloons and a picnic-check tablecloth. The only other little kid liable to be there is ds (who will be 6) but I think I'll make a couple sets of beanbags out of watermelon-themed fabric & he can play "toss the watermelon in the basket". Dd will no doubt gnaw on the beanbags :LOL
For ds's numero uno, back in my more commercalized days, we went with a Pooh theme. Bought Pooh invitations, napkins & plates, balloons in red & pooh-yellow, and frosted the cake with pooh-yellow & red with the words: "Hip hip POOH-RAY! [ds] is 1!"
Other themes we've had are caterpillar/garden, snowman, Lunar New Year (the dragon cake for that one was fantastic, if I do say so myself) and last year, barnyard/Charlotte's Web, with a Wilbur cake.