Garmen is what would be the son of Yamcha and Bulma if they got married in the Android Saga, instead of Vegeta and Bulma.
It all started in the Android Saga, where Yamcha suggests them getting married, 2 1/2 years later they marry. When Goku and the others arrive on the island where the androids would appear, Garmen makes his debut appearance. Future Trunks did not come to help, but Future Garmen uses the time machine Future Bulma invented to travel back in time, to help them defeat the androids.
After Future Garmen's arrival into the past, android 17,18 and 16 are awakened, he tries to stop the duo from escaping but they already have. With the androids looking for Goku. Garmen waits for the fight to continue with the androids. After the androids knew that Goku was in the Hyperbolic Time Chamber training with Gohan, they waited for him to finish. They went to an uninhabitad island not far from the Kame's House, and Piccolo fought #17. Until their fight got interrupted by Cell, looking to absorb #17 and #18.
With Garmen just sitting and watching, Cell mercicly beats Piccolo around and instead of killing him he absorbs his energy and throws him into the water dead. With Piccolo gone there are no more dragonballs, so Goku goes to New Namek and recruits Dende to be the next guardian of Earth. With Dende on Earth he creates another set of dragonballs. After Vegeta lets Cell absorb #18, Garmen gives it his all to stop Cell in his perfect body but he is no match for him. (Seeing as how Garmen can not go Super Saiyan, his power is half of Trunks power.)
With Cell gone waiting for his Cell Games to begin in 10 days, Garmen goes in the Hyperbolic Time Chamber along with his father, Yamcha because they both need to boost their power levels. Ten days later Garmen, his father and all the other Z Fighter show up at Cell's arena to challenge him. After Mr. Satan and his group are done showing off and are defeated by Cell. The Cell Games begin with Goku being the first to face Cell.
Goku was putting up a good fight with Cell but Cell eventually overpowered him. Goku with nothing else to do forfieted the Cell Games. He asked if he could name the next opponent which Cell agreed to. Cell was surprised when he found out that Goku wanted his son Gohan to fight next, Cell accepted and the big fight began. Later when Cell created his seven Cell Jr's. Garmen fought one of them killing the mini Cell with the Ultra Kamehameha .
Later after Goku took Semi-Perfect Cell to King Kai's planet to avoid Earth's destruction, Garmen thought it was over and was ready to leave. Until Super Perfect Cell shot a Full Power Death Beam out of the smoke killing him. The events of the Cell Games happened and the dragonballs were gathered and the first wish was to bring back Future Garmen, the wish to bring Garmen back was granted and Future Garmen was wished back to life. After the wish to remove Android 18's self destruct device, Garmen thanked everybody for helping him defeat the androids and Cell before heading back to the time machine to head back to his own time in peace.
I have to watch the World Tournament through Fusion Saga again to remember what happened and edit it for this page!