I like putting in bits of lyrics to obscure songs (like Shpadoinkle Day), make visual references to bands/musicians I like (did a little mash-up of Meatloaf's Bat Outta Hell and Bat Outta Hell II: Back Into Hell album covers), or giving places and things really stupid names. Like, I named the place my comic is set in 'La Ciudad', which is just 'The City' in Spanish. Or have places like 'Strontville', which 'stront' is supposed to be 'shit' in Dutch, so it's 'Shitville'.
No one really notices any of them, but it's fun for me and that's all that matters. It's funny because my comic is really Super Seriousā¢, but then I have some dumb stuff sprinkled in there for personal entertainment.