Turtles Forever/Heartwarming

"1987 Turtles: It's Ninja Time! 2003 Turtles: Turtle Power!"
 * The Turtles Forever crossover movie, which from beginning to end is a love letter to the Teenage Mutant Ninja Turtles franchise and its fans, ends with . Not only does it bring the whole franchise full circle, making it the perfect ending to a movie that celebrates all the incarnations of the turtles, it's also a touching tribute to the franchise's creators.
 * The 2003 and 1987 turtles part ways and trade each other's catchphrases as a sign of respect.

"I'm gonna miss those fudgeballs...not."
 * Related to above: Raph didn't admit it until they were gone, and, although he tried contradicting himself right afterward, the smile on his face told us otherwise.

"2003 Leonardo: Today, we're more than just allies. We're brothers."
 * Earlier than either of that:

"Splinter: Well done... my sons."
 * In the same vein, there was one line from Splinter before the two teams really started getting used to one another. It was directed at the two Dons, but it would have the same effect with any of the counterpart pairs:

"Mirage Donatello: I'm gonna miss those wannabes. Mirage Michaelangelo: Yeah, I kinda dug the initials on the belt-buckles. Mirage Raphael: Huh. You would. I could go for a slice, though. Mirage Leonardo: There's that place on Bleecker."
 * And, in a sense, the Mirage-Turtles' final thoughts on their adaptations.

"1987 Splinter: Please take this moment to nourish your body and soul, as you prepare for the challenge that lies ahead of you. 2003 Leonardo: Thank you... Master. My brothers and I have found your dimension to be, well, disorienting. But being here, seeing you feels right. 1987 Splinter: To me also, Leonardo. You four are welcome here always."
 * There was also the portrayal of 1987 Splinter. He escapes any of the Take Thats and is portrayed and treated with great respect and dignity.