You were training with Kakarot and Vegeta, when they realized, that even in their blue forms, you were just too strong. They didn’t have potara, so they did the fusion dance, which you enjoyed watching them fail for an hour. They got it right, and after the smoke cleared, this unusually buff guy stepped out. “Heh, let’s see how you handle this!” -they charged up, and their aura turned blue- “Gogeta…. BLUE!” -their hair turned blue, and they got into a fighting position- “Ready?”