There is definitely a place for emotional support animals.  Many people need them to get through trauma, emotional and physical disabilities.  I'm not sure if the individual claims his possum as an emotional support animal or not, but you probably need to be respectful of other people when you bring a wild animal onto a plane.  You can decide for yourself with today's episode of DON'T BE THAT GUY:

Man Gets Booted From Flight For Bringing Pet Possum On Board: The NY Post claims Gerald Tautenhahn made headlines yesterday when he revealed he carried his pet possum on a JetBlue flight from Long Beach, California to Austin, Texas over Thanksgiving. He got booted from his return flight after the crew realized he was carrying a wild animal rather than a cat or dog. Gerald says his possum was never out of her carrier or causing any problems.

I actually like possums.  They're my favorite rat, because they will eat every single wood tick in your yard.  Please, when you're flying, DON'T BE THAT GUY!