EP raises 5bbs
No callers until the button and villain calls 10% of his stack with 55.
Is this a bad call?
Taken in isolation, it's pretty bad. 10% is too much to pay to chase a set.
Otherwise, it all depends. Does the EP opener have a bet sizing tell? There was one reg who would do that, open for 5XBB with (A,K) or (A,Q) and open 3X with everything else, including the biggest pairs. Several times, I'd call with those little pocket pairs, or
hands like (A,x) and (K,x) to see if I could flop a small pair, or cooler him with 2-pair. So long as there weren't any big cards, I'd just let him get stubborn and bluff it off. Unlike most rec-fish, he caught on and quit doing that. (He still does have a bad habit of overplaying big overs and TPTK, so that makes it worth it to set mine him when stacks are sufficiently deep.)
Another time to make this call is if the opener is a "one and done", or a FoF. Then you can take it away on the flop or turn if he doesn't continue without hitting something.