Running jokes from Ed, Edd, and Eddy?
 

I have to make my little cousin an "Ed, Edd, and Eddy," birthday card. I'd kinda like to make some ref to the show other than just have pictures of the main characters. However, I've never seen said show, so is there a certain running joke in most of the eps that I could mention?

Ugggh, it was so much easier when he was into Rugrats

I wouldn't call these running gags, merely reference....
 

1) They always make reference to living on a cul d'sac, never a street or road.

Consider it a jab at living in suburbia.

2) One of the other kids has a best friend named Plank, that's a board with a smiley face on it in Magic Marker (always cracks me up).

3) They all try to emulate the cool kid on the cul d'sac, Kevin,

4) There's a lot of discussion on the internet about whether, I think it's Ed, is slow (I mean REALLY slow, as in taking the 'special' bus).

5) Edd is often referred to as Double D

Don't forget their unnatural love for jawbreakers!