In most instances, I think the simplistic style of the modern TMNT characters translates itself better into the Half Shell Heroes line than it does the standard action figure line. Mutagen Man is a prime example. I was unimpressed by the standard action figure release, but this little guy is pretty cool!
The Half Shell Heroes line is basic in both design and execution. There isn't much by way of paint applications on this little guy, but it works with the chibi vibe he's giving off. I've not seen the modern cartoon that features this guy, so I don't know if his brain/organ parts inside are all yellow like his external mutagen appendages, but I do wish I could bust him open and paint those up to be more organ-like. He looks more like a walking spaghetti squash than a walking canister of innards!
Regardless, I love this little can of goo. He's too ridiculous not to love!
I got Mutagen Man from fellow toy nut Jboy. He was originally released with Kirby bat (Mutagen Man, not Jboy!)