Goku had known about fusion in the Cell/Android Saga

[Pocket-God]

So the aliens he was living with were the same ones that taught him fusion, meaning he knew about fusion already when he came back to earth.

What changes and who do you think would fuse? On that note, was there actually anyone similar enough in height to fuse properly? Then again Vegeta and Goku fused in Fusion reborn so maybe it doesn't matter.

Oh and I guess that means Goku didn't learn Instant Transmission since he wasn't with those aliens in this scenario.

 

[Captain Cadaver]

On that note, was there actually anyone similar enough in height to fuse properly?

Baseball God Yamcha

Tenshithands is taller than both, but the difference is still less than between Galu and Vegeta.

Anyway, Goku likely teaches it to the main cast. When #17 and #18 show up in this version of the original timeline, Yamcha fuses with Ten and Kuririn fuses with Gohan. Even with them not having improved too much since Mecha Freeza's death, I'd say their power would manage to either overcome one of the twins or buy Piccolo enough time to fuse with Kami and help defeat both of them. With the Dragon Balls gone and nobody capable of Shunkan Ido, but the damage to the Earth not too great, the cast learn to accept living without the Dragon Balls and don't build a Time Machine. However, they continue training so as to not be killed by a random threat.

7 years later, Dabura presents such a threat to them. However, Shin would likely show up beforehand, grant the cast the opportunity to train on the Kaioshinkai and whether or not Gohan is able to pull out the sword by the time they are forced to fight, fusion would be enough to win. Dabura is killed and Boo remains asleep. With only 3 Saiyans around, Beerus doesn't have the prophetic dream of Super Saiyan God and remains asleep. Sorbet is still out there, but likely never finds New Namek.
The only question mark is Cell showing up. If he's as strong as in Future Trunks' timeline, he gets easily killed. If the data of the strength of the fused fighters was added to him due to it's significance and boosts his power, he likely decimates the entire cast.

 

[withheldforprivacy]

On that note, was there actually anyone similar enough in height to fuse properly?

Baseball God Yamcha

Tenshithands is taller than both, but the difference is still less than between Galu and Vegeta.

Anyway, Goku likely teaches it to the main cast. When #17 and #18 show up in this version of the original timeline, Yamcha fuses with Ten and Kuririn fuses with Gohan. Even with them not having improved too much since Mecha Freeza's death, I'd say their power would manage to either overcome one of the twins or buy Piccolo enough time to fuse with Kami and help defeat both of them. With the Dragon Balls gone and nobody capable of Shunkan Ido, but the damage to the Earth not too great, the cast learn to accept living without the Dragon Balls and don't build a Time Machine. However, they continue training so as to not be killed by a random threat.

7 years later, Dabura presents such a threat to them. However, Shin would likely show up beforehand, grant the cast the opportunity to train on the Kaioshinkai and whether or not Gohan is able to pull out the sword by the time they are forced to fight, fusion would be enough to win. Dabura is killed and Boo remains asleep. With only 3 Saiyans around, Beerus doesn't have the prophetic dream of Super Saiyan God and remains asleep. Sorbet is still out there, but likely never finds New Namek.
The only question mark is Cell showing up. If he's as strong as in Future Trunks' timeline, he gets easily killed. If the data of the strength of the fused fighters was added to him due to it's significance and boosts his power, he likely decimates the entire cast.

You forgot two persons must belong to the same race to fuse. Gohan and Krillin don't fuse.

 

[Captain Cadaver]

You forgot two persons must belong to the same race to fuse. Gohan and Krillin don't fuse.

Such was never stated. Goku only said fusion required someone of comparable height and power.
Even if this was a rule, Gohan and Kuririn would still fuse since Gohan is half-Earthling and Goku never noted that a fusion between himself and his half-Saiyan son wouldn't work. If anything, the events concerning the Potara actively disprove this, and I highly doubt it was due to their magical affinity overriding such a rule when Super still makes it apparent it's rules are little different than that of Metamoran concerning mortals.

 

[Let's Go Fearless!]

Nah, Goku wouldnt teach them since he's completely confident that he can beat the Androids with his own power. Moreover, he knew the existence of ascended SSjin so he'll just learn that if his own regular SSjin isn't enough.