After the death of the Demon King Piccolo, his spawn, Piccolo Jr, was sent down to Earth in order to get even stronger. Celeron was tasked with taking the son of the Demon King down during the 23rd World Tournament in the next couple years. 

During the training, Celeron pushed himself as far as he could, which did worry Kami that the training was not enough... However, he was reminded of a mentor up in the Afterlife, someone that could push the Saiyan beyond what he's capable of. His name... was King Kai. Of course, he'd need to ask a favor from the king of the Afterlife, Yemma, as Celeron wasn't exactly dead...

Both Kami and Celeron managed to convince Yemma to allow the Saiyan to train under King Kai, since if Piccolo Jr. wasn't stopped, there could be more casualties than there was with the Demon King. 

After a couple of years, during the tournament... Celeron had returned, but something was different about him... As if he undergone a heavy change during his training. And it wasn't just a change of size.