OT episodes with good characterization

[CyberCubed]

The original cartoon has a lot more depth than people give it credit for. If you look past the repetitive plots (which are fun anyway), the characterisation of the main cast and the villains is very well done.

[pferreira]

Originally Posted by Refractive Reflections

I agree with most here that there are many episodes that show a more "3D" side to the characters rather than develop the characters in any particular direction, due to the episodic nature of the show, but there's still continuity to the show since the characters can recall their past adventures. It's still very entertaining because it makes the Turtles more well-rounded than compared to even some of the other TMNT shows.

For example in "Turtles on Trial", "Night of the Rogues", "Dirk Savage: Mutant Hunter", and Season 8 & 9 reveal the ambivalent relationship they have with humans.

OT Michelangelo's warm personality is shown in "Welcome Back Polarisoids" & "Michelangelo Toys Around" (in "thawing" bratty children), acting as an older brother in "Adventures In Turtle-Sitting", displaying his competence in "What's Michelangelo Good For?", and his longing to be a part of humanity "The Gang's All Here".

There are a lot of the individual Turtle episodes that expand the OT Turtles outside of their character tropes:

For Leonardo in "Take Me To Your Leader", "Snakes Alive!", "Leonardo the Renaissance Turtle", "Unidentified Flying Leonardo", "Leonardo Lightens Up", "Leonardo Versus Tempestra", "Beware the Lotus" and "Farewell Lotus Blossom"
For Donatello in "Night of the Dark Turtle", "Donatello's Degree", "The Maltese Hamster", "Beyond the Donatello Nebula", "Donatello's Badd Time", "Donatello's Duplicate", and "Donatello Trashes Slash".
For Raphael in "Raphael Meets His Match", "Raphael Drives 'Em Wild", "Raphael Versus The Volcano", "Raphael, Turtle of a Thousand Faces", and "Mr. Nice Guy".

The OT even expands on the characters of the villains as well. One prominent example is in "The Foot Soldiers Are Revolting" to reveal why Shredder still continues to keep Bebop and Rocksteady around despite their mistake-prone ways. The series gradually displays the strengthening alliance between Shredder and Krang when at first they were extremely distrustful with each other (the first Season, "Turtles on Trial", "Beware the Lotus", "The Four Musketurtles"), and were willing to betray each other in the early seasons, but by the later seasons they seemed to have formed a dependable alliance after so many attempts to destroy the Turtles (in "Get Shredder!", Shredder wanting Krang back even when he assumed the Turtles took Krang; teaming up against Dregg in the 10th season.)

Even Irma shows some development (whether it was intentional or not is uncertain) when in the 2nd to 4th seasons she's used as comic relief for her clumsiness and over-the-top infatuations in dating and romance; by the 6th season, she's taking more of pro-active position in fighting against the villains ("Super Irma", "Night of the Rogues", "Combat Land", "Shredder Triumphant!").

The show has a lot more to offer for its characters than some may think. It's just that this is obscured in the prevalent comedy, many mad scientists, and deliberately absurd and humorous plots found in the series.

That post summed up what I feel perfectly. Especially the last sentence.

[Wesley]

I kinda liked that the Turtles were willing to work together with their enemies when faced with a greater threat. They worked briefly with Bebop and Rocksteady in "The Foot Soldiers Are Revolting". They even tried to help Shredder and Baxter in "Case of the Killer Pizzas".

I thought Baxter was portrayed as a tragic villain, as his mental health deteriorated over the course of the series. Bebop and Rocksteady were shown to be smarter than they appeared to be in episodes such as "Shreeka's Revenge" and "Bebop and Rocksteady Conquer the Universe". April seemed to have a more proactive role in episodes like "The Gang's All Here", "Cry HAVOC" and "A Turtle in Time" rather than being the damsel in distress in most other episodes.