Can somebody help me out lol?

Well i watch family matters all the time, and the other day there was this super funny episode called (TO BE OR NOT TO BE) lmao and it was soooo funny, but anyways, carl turns into a nerd and is sitting on this couch playing some sort of song with some kind of instrument, so i was wondering if you awesome people out there would go under youtube for me and look up to be or not to be family matters and see what song hes playing and what the thing is that he useing to do so, thanks so much if you all do, take care