I have a silly Sonic au! So, basically, every different Mobian species or family(canines, reptiles, insects, felines) have their own language that the animals know at birth. There are universal languages, but they are rarely known among Mobians, so they use sign language for things like bars or movies or groceries where you'd have to interact with people of different species. When Tails meets Sonic, Tails doesn't know sign language, so he doesn't talk much. he stays with Sonic and picks up books on how sign language works and how to communicate with the blue hedgehog. he noticed sometimes he understands what he's saying, but brushes it off. Then, he finds books on interspecies languages, reads the hedgehog chapter and where to find more books on it. after only a month of the fox's hard work and determination, he learns sign language and how to speak the hedgehog language, surprising Sonic by the time it's the blue one's birthday.
