ID:171228
 
Randomly pick some1 in the world to have and overlay(For tag game)
Try to use the pick() proc.

Quoted from DM Reference
Also, to pick a value randomly from a list, simply pass the list as the sole argument into pick(). In this case, there is no provision for weighting the probabilities. All items in the list are equally likely.
Make a new list, loop through the world's mobs using for(), add all those mobs to the list, and then make a new variable defined by using pick(mylist).

Then add the overlay to the new variable you just made.