I've only had two happenings like this.
No. 1: I got called up by the guy that booked my dance gigs at clubs and asked to attend a dinner. The dinner was attended by 11 dancers (from twinks to bodybuilders) for a former US senator. I worked with some of the dancers previously. So the former politician chooses the two guys - a 130 lb. twink and a 145 lb. twink. Being 260 lb. bodybuilder, I guess I didn't have a chance.
No. 2: I was working out at a famous gym in LA on a week day (late afternoon). A guy came around the gym and asked a couple questions. Went up to posing room and three of us bodybuilders were asked to flex and pose for two guys watching us. Then asked to put on red stripe speedos. Two of us, me included, were hired for a pool party mansion. Paid good and extras were available.