There are two symptoms of Tetris Effect, which occur without conscientiously thinking of it:
1. A person can't help but notice how neatly objects in the real world could be stacked together, and imagines a sort of Tetris game in which the objects are stacked.
2. A person visualizes games of Tetris or Tetris scenarios when they daydream, project mental images, or close their eyes.
Note: Such an effect occurs with various repetitive or puzzling tasks, most commonly Chess, Polarium, and Guitar Hero.
Lynch: Yeah, that Popsicle Stand would perfectly fill that space between those two parked cars!
Fisher: What? No, look at those two chicks making out!
Lynch: Oh. Yeah.
Fisher: I think you play Tetris too much.
Lynch: Nah, it's just a little Tetris Effect.