The Teenage Mutant Ninja Turtles have been teenage since the mid 1980s, I think, and as such, they're actually middle aged by now. So then they're really more like Middle Aged Mutant Ninja Turtles. But think of what these now middle aged hero characters could do for advertising!
Yes, now that they're middle aged, the Mutant Ninja Turtles could show how they stay able to fight evil and stuff and keep up their fighting skills despite arthritis and aging joints with glucosamine and chondroitin supplements, and maybe they could even shill for pharmaceuticals like Celebrex. Plus, after years of eating pizza, they might need something like Prilosec.
Plus, most of the early Teenage Mutant Ninja Turtles fans are probably pushing forty now, and so they might really respond to ads like these; or at the very least, laugh at them and remember them.