Boy, this variant will make kickstarter backers like me real happy.
I got the idea after dipping my hand repeatedly into the treasure chest AKA storage box AKA mimic (with industrial tape pasted on the hinge) to draw treasure tokens. Whether you're playing the basic rules or with variant rules, this idea can be applied to any game.
The "You-Might-Want-To-Be-Careful-Putting-Your-Hand-In-There" variant rule
Whenever you would draw a Treasure Token due to opening a Treasure Chest, the Dungeon player rolls a spare dungeon die. If the result is a Dragon icon, the treasure chest turns out to be a Mimic in disguise. Pull away your hand with a horrified look on your face accompanied by some suitable expletive. You do NOT get to draw a Treasure Token. Check for each Treasure Chest separately.
That's it! The game becomes a lot more fun, especially if you're not the active player.
Now for those with the regular run-of-the-mill edition, you may wonder why you can't play this variant with your grudgingly admittedly better-looking storage box?
After much play-testing, I'm sorry to say that it just doesn't work. You will look ridiculously silly being afraid of what is obviously just a vanilla treasure chest. Upon rolling a Dragon icon, the table doesn't even erupt in howling laughter. It's just too much to expect anybody to imagine that such a mundane-looking treasure chest can be a mimic.
So yeah, just turn mimic-green in envy at us kickstarter edition owners being able to play with such an awesome variant.