Goku was on Roshi's island at Kame-house with Master Roshi, Bulma, Krillin, and his 4 year old boy, Gohan.

They were all hanging out before Goku suddenly felt a massive power level

Goku: "Hey, guys. I'm sensing something huge coming our way!"

Krillin: "Are you sure?"

Bulma: "Hopefully, it's someone good."

Roshi: "I doubt it. If Goku's concerned, then it can't be good."