Someone’s standup bit? A movie I haven’t seen? Some internet shtik? The SD itself?–though I don’t think so.
I could also ask where “I don’t think so” (as a way of saying “No, dumbass”) but that’s a whole 'nother GQ. (And where did “a whole 'nother” start, anyway?)
“I don’t think so, Tim” was Al’s tagline in Home Improvement when Tim Allen was suggesting doing something particularly stupid. Don’t know if that was where it originated.
Billy Crystal’s character in Mr. Saturday Night (1992) often used the phrase “Did you see what I did?” following his gags, and David Paymer (playing his long-suffering brother) nods and says “I saw” at least once. No doubt Crystal and the other co-writers of the film were referencing some well-known bit of comic schtick.