Péché d’orgueil

Goten and Trunks attempt to fuse, and their first attempt yields a weird-looking fat kid with very little power. Their second attempt creates an old, emaciated weakling. Finally, the two are perfectly in sync, and make Gotenks. Piccolo tells him to wait thirty minutes for the fusion to wear off so they can try it as Super Saiyans. Gotenks thinks he's powerful enough already and takes off to find Majin Buu. He is able to get some hits in on the monster, but when Buu steps up the intensity, Gotenks is no match and is easily defeated. Meanwhile, on the world of the Kais, Old Kai continues the long ceremony needed to awaken Gohan's hidden power. (Source: Wikipedia)