Oh great!!!!

[Glacier]

Here's a good site with some ideas for getting the possum to move on!
http://www.opossum.org/discourage.html

[dab_20]

I would recommend humanly trapping it, then relocating it. Or scheduled feeding times for the kitty. Good luck!

[Chilli]

I've always thought they were adorable!
To get rid of him, if you don't think you could successfully trap and relocate him by yourself, I say contact a local pest control. The ones around here use safe traps and release them to places away from the public.
Just a thought. Good Luck.