AppearanceEditThe only difference in appearance Mega Buu has from Super Buu is two things. One is a yellow colored Metamoran vest, adopted from Gotenks. Also, his head tentacle is slightly longer than last time. He gains a slight muscle mass, if any. When he finished his transformation into this form, he asked the shocked Gohan, "What do you think Gohan? A new suit to fit my new power."
Absorption and RematchEditWhen it became clear to Super Buu that he wasn't going to destroy Earth with the mighty Gohan in the way, he devised a trick. He gathered all his energy and self-destructed making it look like he tried to kill Gohan, the latter escaped, but in reality he just made a diversion to plan something. When all of the heroes had escaped and gathered around in a safe place, Super Buu made himself be known. Mystic Gohan proposed Buu another match, but Super Buu declined. He instead wanted to fight Gotenks, shocking everyone. But Gohan remained defiant and said Super Buu's fight was with him. He sensed something peculiar about Super Buu's offer. But the Buu remained unshaken and continued to insult the boys, which drove them over the curb and they fused into Gotenks at Super Saiyan 3 form. Then Buu detached two blobs from his body and used it to absorb the freshly formed Gotenks and Piccolo, resulting in his more powerful form- Mega Buu. Gohan remained undeterred saying that he would never back down from Mega Buu. Piccolo's superb mind begins playing tricks on Gohan, and Buu keeps saying things that will not make Gohan fight to his full potenial, like how the Gohan's anger gets the better of him and he engages the new Buu in battle. But he soon discovers that Mega Buu's powers far surpass his own, even at full potenial. He also begins dishing out new moves, like the Special Beam Cannon and the Galactic Donut. After Mega Buu had his fill of testing out his new powers, he beings to charge his Destroy Everything! attack, prepared to kill Gohan, Dende, and Mr.Satan. Hercule foolishly tries to shoot the incoming ball with his gun, saying his friendship with Buu is officially terminated. Out of nowhere, a bright yellow beam clashes with the destructive ball. Tien emerges into the fight, having shot his Neo Tri-beam. He comments on how Gohan has changed inside and out and he's proud of him. He then prepares to stall Mega Buu by attacking him with his strongest attack in Dragon Ball Z, the Ultimate Neo-Tri Beam Barrage. However, there is not even a scratch on the Buu. The monster laughs manically as he prepares another energy ball. He's about to level the terrain when our hero emerges with a timely arrival and cuts Buu with a Destructo Disc. Goku has come with the finest plan to finally bring down the evil Majin Buu.
Mega Buu comments on how "Dad" finally came. He then effortlessly takes control of his lower half. It gives a crushing kick to the unexpecting Tien, knocking him out cold. He then gets ready to battle our hero. But Goku tosses Gohan a Potarra Earring, extrememly mystical objects that will allow two people to fuse forever into the ultimate being. But Gohan fails to catch the small object and goes looking for it while Goku stalls Mega Buu. The duo battle it out as Goku's new Full-Power Super Saiyan 3 form stays on par with the seemingly invincible monster- but is unable to land any critical hits. Mega Buu then reveals he was just he was playing around and charges Goku, preparing to kill him. But suddenly, he yells in pain and transforms into Namek Buu. It's revealed that Gotenks had defused inside of him, making him loose over 1/3 of his power. It is then that he absorbs Gohan and becomes Ultimate Buu.