As a big fan of TMNT myself, I'd like to chime in and give my two cents, albeit a bit late. From my understanding, the original TMNT comics were typically submitted to CGC as comics rather than magazines, although there could be exceptions depending on the specific issue or edition. It's worth noting that there are also some great literary magazines out there that feature comic or graphic novel content. So, that's something to keep in mind if you're interested in exploring the genre further. Regardless, I hope this helps, and happy collecting!
