Raphael: Every minute we stay down here, Shredder gets stronger and Mikey gets more annoying.
Donatello: We're training... sort of. As soon as the sun goes down, it's Turtle time.
Bebop: Let's rumble, baby.
Shredder: Foot Clan, vanish.
Casey Jones: Everything's normal. And the next thing I know, I see a garbage truck, and it starts launching manhole covers.
Rebecca Vincent: What are you?
Michelangelo: We're not really into labels.
Leonardo: Some call us freaks... monsters.
Raphael: Let's just say we're four brothers, who hate bullies and love this city.
Leonardo: Sensei, the Foot Clan are intending to break Shredder out.
Splinter: If Shredder is free, his reign of terror over the city will begin again.
Splinter: Then there is only one question: why are you wasting time talking to a grumpy old rat? Go get him.
Bebop: Hey, do I look fat?
Rocksteady: No, of course not! You look... really FAT.
Rocksteady: Can you smell what this Rock is cooking?
Baxter Stockman: Inside every human, there's a dormant animal gene. This will return them to their rightful place in the animal kingdom.
Baxter Stockman: This is gonna be insane.
Krang: Time for a new game! Look out, Earth, it's playtime.
Rocksteady: You ever see a rhino charge?
Leonardo: We keep failing.
Splinter: Keep the team unified, and you shall always succeed.
Shredder: We meet again, Turtles.
Bebop: Turtles are out, rhino and warthog are in.
April O'Neil: If you want to go down swinging, these guys hit harder than anyone.
Answer: There have been many reasons they maybe didn't want to come back for a sequel. Or sometimes actors are too busy working on another movie and it interferes with their filming schedule.