A Rick and Morty comic almost had a Teenage Mutant Ninja Turtles crossover, although the reasons for it not happening were definitely not very cowabunga. In a retelling of the Emmy-winning "Pickle Rick" episode, the infamous scientist-turned-pickle ends up aware and defenseless in the sewers. As he begins his process of collecting body parts from the slain bodies of the sewer creatures, one of them now includes a baby turtle that someone flushed down the toilet.
In the third episode of Season 3, Rick turns himself into a pickle to avoid going with his family to therapy but his plan backfires, leaving him alone without any pickle serum. He avoids being killed by a cat or the sun but is swept away by rainfall into a nearby sewer drain. Not interested in dying as a pickle, Rick kills a nearby cockroach and uses his intelligence to concoct a makeshift body. He uses this to create a lab where he is able to build a complicated exoskeleton complete with weapons that he uses to brutally kill a group of vicious rats. When the last one is literally nailed to the wall, Pickle Rick uses a jetpack to escape the sewers through the plumbing of a secure compound full of armed guards.
In Rick and Morty Presents Pickle Rick #1 by Delilah S. Dawson and CJ Cannon, we see a similar pattern of events but with subtle changes. Having been discovered and left in the kitchen instead of his workbench, Rick is found by a woodpecker, which picks him up and flies away. Fortunately, the woodpecker's saliva causes Rick to slip out and fall into a nearby manhole where he is left in the sewer amongst the roaches. Foreshadowing the events that will happen similar to the original, the comic allows a heavily suggestive commercial to interrupt before returning to Pickle Rick in his new exoskeleton with pieces of his victims scattered about. Although he doesn't feel bad about the roaches and rats that died, he acknowledges the murder of a baby turtle will definitely weigh on his conscience later. He calls out its previous owner for heartlessly flushing him and acknowledges "Master Splinter I am not."
Rick and Morty is well known for its mix of subtle and over-the-top pop culture references as the show balances satire, parody, and other allusions to the multiple genres it draws influences from. In the Teenage Mutant Ninja Turtles origin story, the turtles were accidentally dropped and swept down into the New York sewers where they were exposed to an experimental mutagen. They were discovered and saved by a nearby rat, the former pet of martial arts master Hamato Yoshi, who was also exposed. The turtles became human-sized mutant versions of themselves capable of speech and martial arts training under the guidance and supervision of their adoptive father, Master Splinter. In this case, Rick discovers a baby turtle in the sewers and instead of protecting and nurturing it, he kills it for his own purposes. Despite his age and intelligence, Rick's desire for self preservation and science is greater than any mercy or sympathy, something that is discussed for its ramifications to his family in therapy.
Although the crossover was denied in the comics, there is always a possibility the heroes in a half shell could make an appearance in the popular Adult Swim show, although considering the show's reputation, it may end in a similar manner. Not only did Rick kill the turtle, he may have also used the head as his mask when he jetpacks out of the sewer into the same secure compound. Although the Teenage Mutant Ninja Turtles comics have shown they aren't afraid to get serious with their stories, they may not be compatible with Rick and Morty's levels of darkness.