Convenient
Autistic Cousin is a (Theoretical) relative, usually between 4-7 year old who is
autistic once you tell someone that you are Autistic.
Allistic
people attempt to use this theoretical relative as a way of saying "You don't look Autistic (Because there is a stigma about relation between Autistic folk and mental disability)" to either invalidate you or as an incredibly bad attempt to relate to you in some way.
Somehow said Cousin is always male and younger than teenage years. Sometimes might be preceded (or followed by) phrase "You don't look Autistic!". Nobody ever actually has seen the cousin in question, Our Scientists believe said
person to be in quantum state where they appear in Allistic mind only when they are faced with reality that the
person they talk to is Autistic; and seems to disappear the moment he (Convenient Autistic Cousin) is no longer needed.