open plank
The mimic is already sigma, but it needs to be ULTIMATE SIGMA! 
make the mimic less obvious - its SO obvious that its a mimic or not.
the mimics should mimic different players - this would make it confusing
make the mimic talk - like it picks a random player and if they talk it makes the mimic say the same stuff. (its like talking into the radio but the radio is the mimics mouth)
fix the mimics movement - they cant just be jumping in a wall, they have to act EXACTLY like a player would.
make the mimic harder to get past - you can walk right into it sometimes and it wont notice you.
mimics should hold different items sometimes - all the mimics should hold different items so its more random
this would make mimics more SIGMA 
timid pike