How did Goku become ssj4?

Answer 1

when he was fighting baby in the GT series he looked at the earth and regretted how he couldn't protect it from baby and said, "earth please give me the strength to protect you." then he started to transform into a great ape except he had yellow fur. this was when pan (his grand daughter) was there...well when goku became the 'yellow ape' pan was scared because she had never seen him like this and also was scared by the fact that he might not turn back to his normal self. well goku was on a tower as the ape and pan flew up in front of him and tried to talk to him. i think he hit her one time and she got back up to talk to him again (goku was over powered and he did't recognize pan) but she eventually got him to calm down and goku turned back into his human form. when goku is ssj4 he has black spiky hair along with a reddish fur coat on the top half the fur does't cover his chest. on the lower half goku wears yellow pants with darkish blue shoes that look as if they are ducked taped to his pants and ankles.

yes it is still goku