Dragon Ball Kai • S07E57 : Rescue Gohan and the Others! Goku and Vegeta's Infiltration Mission!
After absorbing Vegito, Buu notices that he has not taken on any of his characteristics. He guesses this is because he hasn't digested Vegito yet. Inside Buu, Vegito still exists intact, separate from Buu. It turns out that Vegito had planned this, putting up a barrier during the absorption, and letting himself be shrunk by Buu's magic absorption process, but not incorporated into his being