Goku and Vegeta had 1% of their powers inside Super Buu's body.

[Eu sou Perfeito]

Daizenshuu TV Animation Parte 3 e Chozenshuu 3

*Buu sticks his head out of the wall of flesh. Moreover, inside his body, Buu is immortal. On the other hand, Goku's power is less than 1/100 of its original power.*

 

[Hector]

Tosh just cummed to this.

 

[Dagon]

They were shrunken to smaller than fleas. So that makes sense.