Trunks goes back in time because (you) destroyed the world by releasing a virus. All of the Z fighters were infected. (For your own good do not play the voice)

Vegeta the prince of all sayains. so what happened was you ran into him while he and his family were out shopping and he did not like that

Goku is mad because you killed Krillin, and if you find a way to bring him back Goku will spare you.