In the Mirrorverse, Mudd is a clever snake who trades in men (not women) and slaves, and he is ultra rich and powerful. Kirk peeves him and Mudd manages to take over the Enterprise, and ends up leading Kirk and Spock around by chains around their necks on their own ship.
The Venus drug (the Mars drug, of course, now) still acts the same, but Mudd annoys McCoy into concentrating the drug and injecting it into Kirk and Spock in the hopes this will empower them to escape and help him overpower Mudd.
The concentrated Mars drug turns Spock into a fire-breathing demon with a long tail and horns, and Jim into an Archangel complete with white wings and a baaaaad attitude.
What will their revenge be, on both Mudd and McCoy?
Bonus points if the change is irreversible and the two start to find their new forms attractive to each other.