A case of ‘Hey, hey, hey!’ fever

“I’m grown up now!”

That may very well be, but there’s something about Kenan Thompson, be it his wide-eyed enthusiasm, mischievous grin or roly-poly physique, that will always seem particularly boyish. Thompson, 26, is eager to use his current role on “Saturday Night Live” to mature into a performer apart from the children-oriented material (such as his show “Kenan & Kel”) for which he was once known. But such concerns fell by the wayside in the face of bringing to the big screen the character of Fat Albert in the partly animated, mostly live-action adaptation of the same name. The movie is due out Christmas Day.

“It was a once-in-a-lifetime chance,” he says, “so I kind of had to put the age thing aside. I was actually grateful I was still young enough to play it.”

The character’s creator and original voice, as well as co-writer of the film adaptation, is, of course, the legendary Bill Cosby. A Cosby impression is a rite of passage for many young comedians, and Thompson has even done his on “SNL.”

So did he do his Cosby for Cosby?

“I don’t think I ever got around to it,” Thompson somewhat sheepishly admits. “I was doing it subtly to myself, as a joke, but I didn’t think he ever caught onto it. He’s like a mad scientist once he puts his mind to something and that’s what he’s focused on. I didn’t want to throw him off track by trying to impress him with being funny. He’s Bill Cosby, I’m sure he’s heard it all.”