Super Saiyan 5 & Dragon Ball AF
“Super Saiyan 5 is real, and Dragon Ball AF is the next series.”
Somewhere around 1999, a grainy image hit IRC of a silver-haired Goku with fur down his back and wristbands like a wrestler, captioned "Super Saiyan 5." The whisper campaign that came with it: Japan was secretly airing a sequel called Dragon Ball AF, "After Future," and nobody outside Japan had seen it yet. It wasn't Toei. It wasn't even Dragon Ball. It was fan art by a Spanish artist, drawn for a gaming magazine, of his own original character riffing on Goku. The internet did what the internet does best: stripped the credit, kept the drawing, and spent the next decade building fake episode guides and Geocities fiction around a show that was never real. Longest-running hoax in DBZ fandom history, and it started because nobody thought to ask who drew the picture.
Goku Dies of Heart Cancer
“After GT, Goku dies from heart cancer and a Muu Saga begins.”
The other big one. Post-GT rumors insisted Goku was going to die of heart cancer after absorbing all seven Dragon Balls into his own body, kicking off a "Muu Saga" or a "Dimensional Saga" that supposedly ran up to Episode 200. None of it existed. It was dial-up fan fiction dressed up as leaked Toei scripts, and it worked because there was no way to fact-check it in 2001 besides asking someone else who'd also just read it on the same three websites.
Goku Is Literally a God
“A mistranslated guide proves Goku literally became an omnipotent god.”
Somebody ran the GT-era Daizenshuu through Babelfish, got back something poetic about Goku transcending physical limitation, and decided that meant "omnipotent deity" as a hard stat. It meant nothing of the sort. This is less a hoax and more a snapshot of what happens when a teenage webmaster with a translation tool and zero context gets to define canon for everyone downstream of them.