An animated film about ninja turtles who use slang like "rizz" is naturally going to gear toward children. Parents shouldn't worry too much about their kids being exposed to anything unsavory, but some moments push the boundaries of the PG rating. There is language, but it's nothing to be overly concerned about. It's mostly characters saying things like "crap" and "pissed."
The loosest wording used in the MPA's PG rating is "impolite material." This could be in reference to several things that occur throughout "Mutant Mayhem." For starters, there's a running gag that April (Ayo Edebiri) gets nervous when having to speak on camera to the point where she vomits. There are several moments where the audience sees her vomiting in a pretty over-the-top fashion. It's even remixed and gone viral, which may be gross for some audience members.
There's also the body horror aspect with some of the mutants. Mondo Gecko (Paul Rudd) may be a total bro, but Scumbug is fairly grotesque. There's also the final form of Superfly toward the end of the film, where he mutates with various other animals, turning into a Cronenbergian kaiju. It's likely nothing older kids and adults can't handle, but younger children may be frightened by such images. As always, only parents know what their kids can handle, but for the most part, "Mutant Mayhem," playing in theaters now, is fun for the whole family.
