You missed the part where the possum told him to: "...kneeling before the animal and gesturing as though he were conducting a seance."
See, the possum told him to. "Pssst! Psssst! Hey, buddy, could ya help me out ovah here? Yeah, see, I'm in kind of a bind here. Yeah, see, I was minding my own business, trying to eat this half a Big Mac laying in the road and I get hit outta nowhere by a 1972 Chevy pickup. Yeah, see, give me some, whaddya callit mouth-ta-mouth restitution, wouldjya?"
"What's in it for me? I mean, I'd love ta help, but youse don't exactly smell like Dial soap ovah there!"
"Ok, ok, ok, look, I'll give ya a winning lottery number, see? Howzat work for ya?"
"I dunno....how do YOU have a winning lottery number?! Youse ain't even a human bean!"
"Details, details...ya gonna fine-print me on it, are ya? Whaddaya a lawyer is it? Come on, yer a lawyer? That makes us in the same bizniss more or less! Come on, be a pal! Just suck it up and help me out ovah here already! Come on, I'll tells ya where there's a guy what throws away day-old deli sandwiches---even Reubens buddy, ya know, like they usta make over at Morrie's back in the day---if ya helps me out! Come on, whaddya say?"
"Welllll....ok...for that, I'll do it..."