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When you take a shower late at night without knowing what the shower is in aid of, i.e., going out, staying in, staying with company, etc.
For fuck’s sake. It’s 23:45 and I still don’t know if we’re going out or not. Best have a mystery shower.

00:00... she said she would call around now. Best grab a mystery shower.
by JAMwIsE May 20, 2017
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