Embrace the madness: that genie's out of the bottle
Mimics are an iconic monster/trap in D&D, and have been for about four decades. There are a variety of memes and jokes associated with them, including this one.
As a player or as a DM, don't be annoyed by player paranoia. Roll with it
...your arrows bounce off of the chest...
and proceed with the narration. Keep your own focus; that's a thing that you can do.
Actionable suggestion for a DM: don't use gratuitous mimics
As a DM, rarely use them, or never use them, if you find their existence in the game world to be a problem. You never have to have one in your game. They aren't a required monster in your game world.
- If you do use one, place it with care. Make its location and existence fit the scenario that you have created. Mimics survive because they surprise things and eat them.
You can't stop players from some meta gaming.
As the memes, and jokes, that your players have access to spread via word of mouth, reading the books, or at various internet sources, you'll only frustrate yourself if you try to control that. Save yourself the effort.
The same is true for lurker's above, animated armor, gargoyles, rugs of smothering, and various plants that come alive to eat the PCs.
Hey, look, I found a magic carpet! Let's go flying!
oops, rug of smothering
A note on Lore, meta gaming and mimics (and similar monsters/hazards):
As the DM, you control the spread of lore in your world. This kind of "general" versus "specialized" knowledge would include a sense of 'how well known is the existence of mimics' (if it is known at all) in this campaign world? @TimothyAWiseman points out that if your world is one in which the existence of mimics is well known, then testing for them is (1) not metagaming, and (2) is a valid in-character action by any adventurer and should not be seen as an obstacle to play.
