Along with the Mutagen Man figure I posted about earlier I was able to acquire a couple more original Teenage Mutant Ninja Turtle figures, including Rocksteady!
It has been a long time since I've seen an original TMNT cartoon so I'm not sure of the exact storyline, but as I recall the Rhinoceros Rocksteady, along with the Boar Bebop were the first two mutated villains in the TMNT cartoon.
All heck broke loose after that with the Teenage Mutant Ninja Turtles battling mutated villains from all level of flora and fauna, but Rocksteady is one of the first and holds a fond place in my heart. It's a shame he and Bebop haven't been given their respect in any of the number of TMNT films that have been made. Here's the meeting I would have loved to have been a part of, to punch the movie executive in the face: "Vanilla Ice, yes...Rocksteady, no. OUCH! He bwoke my node!"