Marc Cram became a regular character on Kenan and Kel during seasons 3 and 4.
The first time the character appeared To Catch a Thief (even though Marc had first appeared in The Chicago Witch Trials), he was seen at Kenan's house talking with Kenan's parents. He was revealed to have been the spelling bee champion. In Kenan's room he found a 1952 watch. Kenan told him that his father gave it to him. The next day, Kenan's watch was gone, and he thought that Marc took it. So Kenan and Kel went into his house and took his jewelry box as payback. It turned out that Kel and Roger Rockmore had went and took the watch to be repaired (the band was broken.). Roger offered to pay for the damages done to the house when he got covered in orange paint (from an earlier trap).
In his second appearance Happy B-Day, Marc, he invited everyone but Kenan to his birthday party.
In his third appearance Picture Imperfect, he was the assistant to his yearbook photo teacher. Kel destroyed the last names that started with A through L's photos in the darkroom, so Marc, Kel, and Kenan had to go and retake the photos. Eventually they scheduled a event at Rigby's to take a picture with Bill Bellamy, but that went wrong when Kel's photos were pointed at Bellamy. Then, Kel turned on the lights in the darkroom, shut them off, and destroyed the photos that were from M through Z.
The name Marc Cram is a palindrome, meaning it is spelled the same way forwards and backwards -- a nod to the fact that Marc was a spelling champion.