Blatently obvious. If a fat person tries to sneak round a corner they will be seen, as their belly will protrude first and give them away. Hence if something can be seen a mile off, or is really obvious, it can be 'seen coming like a fat man round the corner'
Phil: 'Hey, did you hear Janice was fired?'
Butch: 'Yeah, I saw that coming like a fat man round the corner!"
a pointless-story-ending, similar to "and then i found ten dollars." when your story went nowhere, you put this on the end to make it interesting. generally used satirically to admit story-telling defeat.
cammie:well then it looked like the car had a scratch, but then it didn't really...
lila: cammie, is this story going anywhere?
cammie:...so i saw this chick, and i wanted to talk to her, but then i didn't...and that's when i saw the blood...
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"