Swamped

"Name's Evan among friends, but they'll go by any number of other names. Real good at impersonation. Sometimes they dress up as a local pol as part of the show, either to flatter 'em or to roast 'em. But usually they just blend with the crowd and pull stunts suddenly between acts."

"Stunts?" you ask. "Like, what, pranks?"

"More like pretending to be a heckler. Or sometimes a drunk. The main idea is to keep the crowd occupied while the actors get ready. Though I did see one time when they all of a sudden got up and started juggling."

"So, you want me to watch whoever makes a scene when the first act ends?"

They shake their head.

"No, you'll want to be watching 'em ahead of time. Around ten minutes before the end of the act, they'll do a quick peek at their lines - doin' their best to hide it, of course. Enough time for you to find a reason to leave and, for example, sneak backstage."

"And how am I going to know who it is if they'll be disguised?"

"Their eyesight's not so great," the informant says with a smirk. "They'll have reading glasses to look over their lines, and they always wear 'em to begin with so they don't have to fumble with 'em when they check later. All right, think that's it, good luck."

They walk out before you can even think of any other questions. You suppose that's it, then. You head back into the bar and glance around to see who's got glasses on.