I get the joke, but with no prior context it’s kind of a jerk move to assume the player already opened it if they asked for a perception OR an investigation. A Mimic would normally just ambush you OR attack when the player opens them. If it was opened it’s probably already attacking, and if it was closed then performing a perception shouldn’t cause initiative until rolled (if the mimic noticed you noticing it, for instance).
I’ll…I’ll crawl back into my dingy nerd tavern now…
I mean, any GM who is having you roll either of those to see inside of a chest anyway is a bad GM.
An actual exchange in a group my wife was in, back before we were even dating:
Player: “I wanna catch the stone from his sling! What should I roll for that?”
DM: “Damage.”
"It was at that moment, I realized I had two options…
A.) I can sidestep the projectile, negating any damage entirely…
Or B.) Intercept the projectile, catching it in mid-air, with my face!
OOF!..Should’a gone with (A.)…!"
