Answer:
No aliens are known and proven to exist.
No alien has ever been proven to have examined anyone.
No UFO ever seen is known and proven to have anything to do with aliens whatsoever. "UFO" means you don't know what it is. It is not an acronym for "alien spacecraft".
It's fun, and sometimes lucrative, to pretend there are little gray perverts running around disturbing *other* people. Kind of like a scary ride at an amusement park. The fun would go away if you had reason to think there was real danger to yourself.