My favourite is the mimic accidentally/on purpose placed inside a bag of holding. Any time the party take something out of it there's a nonzero chance it'll be a mimic instead of what they were after.
I think this is pretty funny but depending on your players, they might check all 3 for mimics! Some of us were traumatized once and now we are very suspicious…
@plum This is the first time a Mimic I placed that was successfully triggered, and this particular group of players didn't vocalize any suspicions on the book being the Mimic. We ended the session with joking that everything is now a potential mimic, especially that rock over there, or perhaps that Stalagmite, maybe even my sword is a mimic now.
I just gotta patiently wait for the Mimic funny business to calm down before I place another one, muhahahahaha.