Ahaha… counterstrike. After THAT game, I’d be looking around thinking “This place would be a bitch to secure…”
I used to get this with Snood, too. My Snood addiction started the same summer I started grad school, and I had no computer at home yet, so I’d stay at work until almost midnight, playing Snoo-- I mean, writing articles for class. I’d get on the subway to go home, and I would see Snoods. I’d close my eyes, and I’d see Snoods. BA boop. It was mostly the purple one, which was odd, because I always like the little fluffy blue one best.
During my Tetris phase, I would look at the tree in my parents’ yard, and instead of the beauty of nature, I would see Tetris patterns.
I have just started playing Black and White, and while there aren’t any afterimages yet, I did catch myself singing that damn eidle eidle eee song about a million times yesterday. Help me.
When I have been playing first-person shooters a lot, I catch myself side-stepping around corners and automatically figuring out where I could take cover from the people around me.
That got even worse for me after I started play “Thief.” I’d feel accutely uncomfortable when not standing in a pool of shadow, get the urge to pick people’s pockets and blackjack them when I was done. 
Badtz Maru’s post got me to thinking.
Why the hell can’t we have afterimages when we’ve had sex with someone? Now that would be something.
Of course, watching someone walk around with an idiotic spaced-out smile on their face for an hour or so might get annoying.