For Cash's 5th birthday, we had a Lego theme. I would have ordered these except the seller was in Australia! Alas. But I totally copied her design for the invitations. (And the idea to include knockoff Lego men in the goodie bags.)
Each kid got a personalized Lego tag, which is the zenith of how far I will go craftwise:
Zoe's party was at the skating rink. SK8TE Party, yo!