The first time Goku lost his tail on the Dragon Ball anime is when he transformed into a Great Ape during a full moon (long story). The tail is the cause of this transformation, so Puar shapeshifts into a giant pair of scissors and snips it off during a battle, returning him to his regular form.
During the Pilaf Saga in early dragon ball, when Goku turned into Ozaru, his tail was cut off by Puar, who turned into a pair of scissors.
Having Puar transform into a pair of scissors, Yamcha snips off Goku's tail to bring the Monkey King down to size for the very first time. Goku's tail would regrow during the events of the 21st Tenkaichi Budokai (likely brought about due to the stress of fighting Giran.)
Goku's tail never grows back because, kami permanently removed it when he was training on the lookout, as he wanted to restore the Moon, but didn't want the threat of an Oozaru(Great Ape) to be present.
Why did Vegeta remove his tail? Way back in the Saiyan arc, Yajirobe sliced off Vegeta's tail in order to undo the Great Ape transformation and prevent him from killing the heroes and destroying the world.
After the Cell saga Gohan stopped training and focused on studying. This results in the moon getting blown up and Gohan's tail is removed. Goten and Trunks (and pan and bra) were all born without tails. Goten and Trunks were both born without tails, which was never explained within the story of Dragon Ball.
Think about it this way; Gohan, Goten, and Trunks are each half-saiyan, half-human. They each have one fully Saiyan parent, with the genes for a tail, and one fully human parent, with no tail genes.
Lastly, Goku's tail was permanently removed by Kami at the end of Dragon Ball, but it was regrown by Old Kai's tail-pulling technique in Dragon Ball GT to increase his power and grant Goku access to the Golden Great Ape and Super Saiyan 4 transformations.
But why? All Saiyans are born with tails, which allow them to transform into a giant monkey called a Great Ape. In this form, the Saiyan is unable to control himself -- with the sole exception of Vegeta -- and is usually depicted as an unstoppable force.
Saiyans have a naturally FAST mestabolism. It's way faster than a human's by a long shot. Saiyans are also a very active race, usually busy conquering entire planets. They need to gain a lot of energy, so they eat a lot of food.
It was mentioned early in the Dragonball that Goku felt stronger with his tail, if Goku had his tail now he might be a tad stronger.
Gohan loses the use of his arm in his final battle with Cell when he tried to save Vegeta from a blast intended to kill him and Future Gohan loses his arm completely after protecting Trunks from the androids.
Overview. Halos are a mark of the dead; someone who has died, but has been allowed to keep their body, is given an Halo automatically. When Gokū went to train under the Kaiō of the North, he had an Halo above his head.
In chapter 425 of the Dragon Ball manga, Videl has cleverly unmasked Gohan as the Great Saiyaman, and explains to Gohan that she has deduced this based on Gohan having the same family name — “Son” — as a previous winner of the Tenka'ichi Budōkai, Son Goku.
The Medical Machine permanently closed up Vegeta's tail glands. The Medical Machine (healing chamber) heals and seals all wounds. Since a missing tail is a wound, it was sealed up permanently. So if Vegeta had not gone into the Medical Machine, then his tail would have regrown (but, he would've died).
Even as a grown man and ruthless warrior, Vegeta was able to change his tune thanks to the good influence of Goku, Bulma, and the rest of the gang - proving once and for all that not all Saiyans in the Dragon Ball franchise are inherently evil.
"Saiyans are a warrior race, so their aging slows once they reach an age suitable for fighting, and they maintain great strength for a long time. However, their lifespan is not much different from Earthlings', and when they reach a certain age, they rapidly grow frail," Toriyama said (via Kanzenshuu).
Yamoshi is the first known Super Saiyan in the history of the 7th Universe, having used its power to lead a rebellion against the other Saiyans. Despite the strength of the Super Saiyan form, Yamoshi wore his stamina out, resulting in his inevitable defeat.
Five years later, Goku meets his evil older brother Raditz and learns about his heritage.
When Goku transforms into a Great Ape in the 1997 Dr. Slump remake, Goku is briefly seen as a Super Saiyan/Great Ape hybrid during the transformation. While the form is referred to as "Great Ape", apes are distinctive from monkeys due to a lack of a tail.
Gohan always had the most potential out of all the Z-Fighters, but his lack of training and commitment always hindered his growth, while Goku instead keeps getting better. According to Piccolo, however, Gohan can still surpass his father.
Gohan must've gotten lucky with his tail, as he's the only half-saiyan on Earth with a tail. We know as a fact that pure-blooded saiyans (from Universe 7 that is) are always born with tails, so that biology must get a bit messed up when a saiyan has a child with a human.
well gohan cannot go ssj or beyond becuase all of his power has been put into his base form. meaning that he cant tap the next level of power becuase there is no next level.
The Super Saiyan form can't bring out any more of his power if he's already using it. Gohan's plan is to get stronger by focusing on his Ultimate form, which means that he's unlikely to ever achieve - or even attempt to achieve - the Super Saiyan God or Super Saiyan Blue transformations.