My latest hyperfixation is Rise of The Teenage Mutant Ninja Turtles
Raph and Donnie are the ones I've latched my angst claws into, but this post isn't about angst for once
I imagine that, since none of the turtles were forced to conform to human societal norms: they're all very comfortable with their neurodivergent actions
One thing they do, and have always done, is vocal stim. It's usually unconscious, but often the turtles make a variety of weird noises for different reasons.
This is something Splinter definitely had to get used to and not read too much into.
Happy noises usually include chirping and purring-like sounds. Donnie in specific has been known to click his tongue which can often be heard repeated from the other turtles if they're in hearing range. (April, at first, was very confused by the clicks but has now joined the chaos and joins in with her own click when shes around. Sibling solidarity :D)
Tired turtles often means involuntary whines and groans. That also goes for if any of them are wanting attention. Leo is the worst when it comes to his dramatics, often pressing against his target and letting out heavy sighs until attention is bestowed upon him.
Mikey hums the most, and Raph's few nonverbal moments are communicated through grunts.
All these noises only happen when they're comfortable, though. In a safe place around safe people. It's just how they bond