If Hamato Yoshi had been younger when he mutated into Splinter, he might have looked more like Rob here.

Yep, I am familiar with the Teenage Mutant Hero Turtles, which are the Teenage Mutant Ninja Turtles here in their native America. I first got into the Turtles from watching some episodes of the 1980s animated show. I also got to read a little of the original comic book the Turtles came from, which was darker than the 1980s show and Splinter's origin story was slightly different. Originally Splinter and Hamato were different characters, with comic-book Splinter originally being a non-anthro rat and comic-book Hamato being his owner, who got killed by Shredder. Rewriting the TMNT origins so that Hamato mutated into the rat Splinter was due to making the Turtles show more kid-friendly. I also got to see the 1990 Turtles movie with the Jim Henson suits, which I liked.

Anyway, there have oddly been a couple of time before I created Rob, I fantasized a little of how Splinter may look if he had no top clothing. I would imagine he might have a little muscle build to him. But due to his thin elderly frame, he not as big as Rob's muscles though.