Because I've not made enough Bebop and Rocksteady figures to last a lifetime. I needed some to replace the woefully underscaled Playmate options.

Bebop was made of a Marvel Universe Hulk figure, combined with the head of the current Bebop figure. Rocksteady was a Incredible Hulk Leaping Hulk (which apparently was intended as a 5 inch line), combined with sculpting, paint and a current Rocksteady head. There is a decent size variance between the figures, because let's be honest, Rhinos are larger than Boars, so it makes sense.

I initially blended the heads into the bodies better, but realized I didn't want to sacrifice the neck articulation, and most angles it's not obvious that they aren't exactly lined up.

The last pic is a action-y shot that shows the scales in comparison to the TMNT figures.