Scenario: You're sitting on a the subway on the way home from work when across the car you see a guy and think Holy shit, that's Brad, the guy who I wanted to make out with all freshman year of college. You literally haven't seen Brad in nine years. You barely even remember his name, but there he is on your subway car in spitting distance.
How To Handle It: There's only two ways to play this one; either you approach Brad and strike up a convo (at the risk of him not remembering you at all), or you let Brad get off at Times Square and wonder What If? forever. Personally, we prefer the former, but even if you choose the latter, this is still a GUM.
What It Might Mean: Life is not a rom com. as you've probably figured out by now. While there may be the slightest chance that you and Brad are going to fall madly in love, there's a better chance that you were just supposed to run into Brad. Either because he is a point of access to a time in your life or a part of yourself you've forgotten, or because he's going to lead you to some important information in your life now.