Crocodile Dundee/WMG

Crocodile Dundee is the half-mortal offspring of Bamapana, a trickster god from Aborigine mythology.
This would explain why he was raised by Aborigines (who wanted to teach him the clan laws that Bamapana violated), why he has such a close synergy with the bush (as his bloodline comes directly from the Dreamtime), and his affinity for pulling pranks on his foes. And he's a ladies' man because, well, his father was Bamapana. Demigods are just like that.
 * Except he's not that much of a ladies' man. He makes mention of almost getting married once, chats with some hookers and (eventually) marries Sue. He's certainly charming enough to be one if he wanted to though.

Mick isn't just smarter than he looks, he actually is a genius
From the beginning it's established that Mick is very smart, smarter than he acts, but from the very beginning of the movie there's almost no situation he isn't totally in control of. He only gets better in the second movie as he's more acclimated to city life and is even something of a psuedo-celebrity due to his antics and charm (he gets away with blast fishing on the Hudson!) and after he and Sue retreat to the bush due to the threat on her life he spends the entire second half dicking around with the druglord and his mooks when he could easily take them out quickly. He does this because he's constantly two to three steps ahead of everyone and gets bored easily, the only things that manage to challenge him are convoluted soap opera plots and psycholgical mind games.

Sue, the wealthy daughter of the publisher, was in Australia trolling for a new toyboy (with her dad's permission).

 * This is the only reasonable explanation for how she ended up taking an extended vacation alone with a wild man.
 * This also explains why the paper would pay for him to stay in an expensive hotel when she could have put him up in a Motel 6 and he wouldn't have known the difference.
 * By the middle of the movie, she already understood he was exaggerating everything and she just wanted a plaything.
 * He figures it out a lot faster than that, which is part of the reason why Mick continually teases and screws around with her. By the time he figures out she not only has a boyfriend, but is about to be engaged he's had enough with the games and decides to leave on Walkabout again.

the reason Sue wore that thong leotard under her skirt was because it was really hot outside and she wanted to keep her bottom cool.
or maybe the actress just wanted to show off her amazing ass