In the original timeline. Son Goku was able to ascend his SSJ3 a year before his return to the living world. But what if... What if Goku ascended even further, what if Goku achieved super Saiyan 3 a year early?
AGE 774.
A lot has happened in the last few hours since Goku returned to the living world. Vegeta going under Babidi's control just for a power boost to defeat him while in middle of their fight, Majin Buu was released and because of that Gohan is now presumably killed but Vegeta realized his mistake & sacrificed himself to destroy Majin Buu and atone for his sins... That didn't work, Goku taught His second son: Goten and trunks the fusion dance in Kami's lookout however before they could fully learn the technique, Babidi and Buu learned where Trunks lives. Bulma begged Goku to save her parents and of course the dragon radar since the materials made for the radar is very rare and if it gets destroyed, there would be no chance of finding the dragon balls. Goku agreed to stall Buu for Trunks to get the dragon radar.
Goku confronted both Buu and Babidi as Trunks went to capsule Corp to get the dragon radar. Goku showed the basics of super Saiyan to the majins, the SSJ then SSJ2, SSJ3 which shocked Babidi (and everyone who can sense Ki) with how much power SSJ3 has, SSJ3 power was so intense it shooked the whole planet and Gohan whose currently training in the realm of the Kais to defeat buu felt Goku's Ki... However Goku wasn't finished
"one more bonus..." an smirk formed in the Saiyan's mouth.
Goku begin to power up his Ki once more, the electricity around Goku's golden aura intensified so much that clouds begin to struck lightnings. Goku's long hair were blown by the intense wind he was making.
Meanwhile back in Kami's lookout
Everyone had their eyes closed since Babidi was showing everyone in the planet watch the fight. Krillin would sound shock in fact everyone in the lookout were shock, He thought Goku only had three but there's another one?
Meanwhile in the otherworld.
"YOU IDIOT! SUPER SAIYAN 3 IS ALREADY COSTLY ENOUGH WITH THE ENEGRY, YOU'LL LOSE ALL OF THE TIME YOU HAVE LEFT IF YOU USE THAT!" King Kai through a telepath tried to warn his student but Goku had already made up his mind. Goku was dead and currently He is using his 24 hour visit to the living world but if he uses something that's very costly with energy then He'll lose the time much faster.
Back to Goku & Buu.
Goku's teal eyes turned red and He took off his top Gi, Babidi scared at the ever so raising Ki from Goku, ordered Buu to stop Goku but Buu's child like curiosity got the better of him.
"AHHHHHHHHHH" Goku's scream had a echo then suddenly there was a large energy engulfing Goku, it was so large the energy can be seen & sensed from far away planets heck even a sleeping god of destruction felt something but his time of awaken is not upon yet so he doesn't wake up. SSJ3 had so much power but this, Nearby cities couldn't withstand the power and crumbled under the pressure.
Then finally the energy disappeared and Goku's form was revealed to the world. Goku had red hair/fur, red eyes. His tail somehow had regrown, His forearms were big almost gorilla-like. His expression stern & determind.
"this is super Saiyan 4. sorry it took abit I'm not used to this yet" Goku has one plan. Stall Buu, sure he has the power to beat him but he wants the new generation to beat Buu. The Majin pointed his hand at Goku with a sinister smile.
"You look scary but Buu not scared." Buu stated.
Babidi was understandably scared, The Power Goku was radiating was intense but He quickly calmed himself in order to look confident. "Piffle! level 4 my tailbone. Finish him off, Buu!!" The Warlock ordered. "Heh! heh! heh! Humiliate him while the whole planet watches!" Babidi was trying to look confident as he was using a telepath so the whole planet could watch.
Buu barely moved closer when suddenly Goku appeared in front of the Majin and punched him but Goku grabbed his antenna so he wouldn't flew away.