Im Strong, Like Da Hulk
This comes from the classic "Mr. Show with Bob and David" sketch The Bob LaMotta Story. In it, Bob (David Cross) is being raised by two mentally retarded parents (Bob Odenkik and Jill Talley). The principal (John Ennis) calls the parents in for a meeting, where they shout nonsensical things like "My shoes hurt!" and "I wanna be expelled!" At one point the dad raises his fists in front of his face and says "I'M STRONG, LIKE DA HULK! GRRRRRRR-AAAAAARRRR!!!" So when someone in a screengrab holds their fists up like this, break out this fun reference, sit back, and wait for the cash to roll in.