Idiomatic expression; English.
Definition: When someone says something and once it's heard, it breaks your preconceived notion - e.g. you can never "unsee" or "unthink" it. When someone "smashes the mirror" you can see something for what it is or think about something in a new way counterintuitive to the previous way of thinking.
1. In HIMYM Ted meets a previous ex-girlfriend who talked so much, she ended up with a deaf husband. He then signed, 'Boy, she sure does talk a lot, doesn't she?' Thus you smash the mirror.
2. "Have you ever noticed the negative space in FEDEX makes an arrow?"
"Dude you just smashed the mirror for me."
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