Just got back from the TMNT 35th Anniversary showing at my AMC. I wasn't a Turtles kid (aside from Transformers, it was a side of Thundercats), and I'd never actually seen the 1990 movie in its entirety - just chunks of it back when I had SciFi Channel available in college. My only other experiences with the Turtles have been random cartoon episodes here and there back in the day, and the comic crossovers with Usagi Yojimbo.
And as someone who's relatively franchise blind, that was damn good PG Action Movie fun. It shows its age, but the Henson animatronic costumes and puppets were wonderful, all the gloriously goofy Hollywood Ninja tropes, just enough backstory to tape it together...that's a lot to pack into just under 90 minutes! I kinda love how low the stakes are, honestly - the mighty Shredder is running a grab-and-smash gang of disillusioned teenagers, why? Simply because money, presumably! Casey is just some random masked vigilante, no tragic origin required! Why is there radioactive ooze in the sewers of NYC? It's just there to drop turtles in and get the backstory done! Refreshing, really.
The anniversary showing also comes with five or ten minutes of behind-the-scenes stuff, mostly shilling for a crowdfunded documentary, but it was still neat.