Mimic and adhesive.

[Oryan77]

Can a mimic turn into a rug? If so, do creatures automatically stick to it if they step on it? Or can a mimic choose to let someone walk on it without using its adhesive ability? I'm unsure if the mimics adhesive ability only works when it actively tries to slam attack or if a character sticks to it from merely touching it (opening the "chest").

[Necroticplague]

Can a mimic turn into a rug?

Well, looking at both the flavor text and the mimic shape ability:

A mimic can have almost any dimensions....A mimic can assume the general shape of any object that fills roughly 150 cubic feet
So yep, a rug is definitely within its abilities. Since rugs are rather flat, it would need to spread itself over a wide area to maintain its volume, but it's definitely possible.


If so, do creatures automatically stick to it if they step on it?

A mimic exudes a thick slime that acts as a powerful adhesive, holding fast any creatures or items that touch it.
Yes. Stepping on it would involve touching it.


Or can a mimic choose to let someone walk on it without using its adhesive ability?
If it has adhesive, it's automatic, and it doesn't have any choice. However:

mimic can dissolve its adhesive at will.
So it can dissolve its adhesive to let people pass, but its ability to do so isn't selective. If two people are both are touching it, they're either both grabbed, or both fine.