Previously I did not think they were teenagers, at least they were at least older than 15 years or over 20 and, how Leonardo being the oldest and the youngest Michelangelo if they are the same age? and I thought that they just called Ninja Turtles.
In the new live-action film (2014) they are very tall, about two meters high to be 15-year-olds.
How do some of you know they are 18-19 in the movie TMNT (2007), I tried to figure it out yourself.
The day the turtles were born, Leo and Raph raced to be the first to hatch with Leo winning by a few seconds, thus making Leo the oldest and sparking Raph's rivalry with him. Donnie hatched sometime after that. Mikey was born after Donnie, hatching a little late, which would explain why he's a little uh...odd? But still adorable of course. 15 Years later they became the Teenage Mutants Ninja Turtles!
And that is the story how the turtles were born, The end.
The new movie makes them look like they're in their late teens like 16 or 17. I'm sixteen and I feel like they're at least as old as me. In the 2012 cartoon, they act and look younger so it fits that they're fifteen there.
Yes, I like teenage turtles actually acting like teenagers. :) But I'm also a little disappointed that they're not being allowed to age after three and a half seasons. Being teenagers makes them psychologically interesting, but I still want them to gradually age and mature. When will their 16th mutation day be?
And if you go by Tales of the TMNT, their lifespans are actually centuries-long, with Swan Song telling some of the rest of Leonardo's later life story until his final years. Archie TMNT seems to agree in speculating that the turtles will actually live centuries. IDW TMNT hasn't gauged the lifespans of their actual mutant bodies, but its newly introduced version of Leatherhead is already over 200 years old.