how did the turtle become humans

I don't remember them ever being human, but they got mutated by some chemical and learned to talk and got trained by Master Splinter. Their first food was pizza and their first word was 'KOWABUNGA!'

They touchedooze from a broken cannister

they turned human because donnie made an unstable chemical compound . and mikey + raph were fightin'( didn't c dat comin' ) + they knocked over da compound . they got covered by it + da nxt thing they kno they'r human . ( but , w/ a lil' draw-back . unless u happen 2 like 1 of da characters . they r not clothed . ^.^)

well, if you mean how they became mutants....then they were the pets of a little boy and he dropped them down the drain one day when he was outside, and later on, a canister of ooze fell into the sewers and smashed open, covering them in it, that's when they began to mutate, same with master splinter

Because the Turtles came in contact with a chemical substans, called mutagen, which transformed them to the last thing they came in contact with, humans.

As infants, the turtles lived in a sewer below Manhattan. Toxic chemicals were illegally disposed of via sewer systems, and turned the 4 unrelated brothers (and estranged sister, Venus) and Splinter evolved into humanoid creatures.

I don't ever remember them becoming "human". I've read some fan fiction about them becoming human, but wasn't aware of them doing so within the TMNT world. I saw the very first TMNT cartoon when they FIRST came out and have stayed with them throughout the entire time. The Turtles' first word were pizza, so this nonsense about them "tasting pizza for the first time" on these "new" cartoons are complete BULL. I'm more of a fan of the TMNTs' first movies and I love the TMNT 2007 movie! When did Raph's eyes become GREEN, and Leo's blue? The only one who's supposed to have blue eyes is Mikey. That has always tied into his being the youngest and the "baby of the family". It's all just a part of his charm. I've never like the Umtroms, either. Freaky, little brain-thingies!

Canister of ooze, turtles got covered in it (including splinter), and they mutated. in the 1987 cartoon, a boy was carrying four turtles in a bowl with water, he stumbles, and drops it, which breaks and sends them into the sewer. you know the rest!