The mutagen in the Eastman and Laird's Teenage Mutant Hero Turtles Adventures comics once mutated Hamato Yoshi into a humanoid rat, and Donatello, Leonardo, Michaelangelo and Raphael into humanoid turtles.
Hamato Yoshi's transformation into Master Splinter and the hatchling turtles into the Hero Turtles is told in the TMHT Free Mini Comic.
During the adventures in the TMHT Poster Mag issue 4, Bebop and Rocksteady find a leftover container of mutagen and decide to pour it over the Turtles. Before they can do so, the Turtles chase them out of the sewers. The open container of mutagen is left behind and an egg dropped from a alien galactic transporter falls into it. The egg grows and then hatches into a giant baby dragon. The sweet baby is a menace and rampages through New York City, happening upon and trashing Shredder's temporary base of operations. Inside, Donatello finds a spray canister of anti-mutagen and uses it to return to giant dragon to its normal small size.