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A mildly contagious disease that has a person compulsively singing all star just for the sake of memes. People suffering from smash mouth syndrome may also sing It because the can't get over how catchy "all star" is.
1: Why does he keep singing All Star? Isn't everyone tired of that song?
2: He has Smash Mouth Syndrome, just don't acknowledge him in any way.
1: but he's even doing the voic-
2: shhhhhhhhhhhhhh

3: why did you call it smash Mouth Syndrome if that's the only song the-
2: shhhhhhhhhhhhhhhhhhhhhrek
by TheCupIsHalfBowl March 28, 2017
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