Smart of the fan to show up in a basketball jersey on the off chance he'd be asked to take the court. I have attended quite a few games, and seen many of these bright-eyed youngsters properly clad for game action and eagerly awaiting the tap on the shoulder.
Yet, aside from a Harlem Globetrotters game or a halftime contest, you just don't see them getting pulled onto the court much. Thankfully BB helps restore those expectations to their proper level. Be prepared. You never know.
You know, they may have been given the jersey as compensation for playing in the game. One of my best friends once appeared in a semi-pro game for an indoor soccer team that his friend was on / running /some way involved in; apparently they were short of players so he signed a one-game contract for the jersey. He also got red carded pretty early for retribution after a hard shot by one of the opponent's players.
This reminds me of a great story (well, I like it, anyway) ...
A couple decades ago I was a young sports writer at a small paper, and we covered whatever came to town. The local fairgrounds brought on a "professional" roller hockey team that arrived with a decent bit of noise. So we went to the pressers and wrote all about them, and I covered their first couple games. I wasn't impressed with the so-called professionalism, but news is news. They were selling tickets and playing games, so we covered it.
They were a little shady when it came to rosters, however, and I soon discovered that several players were being signed to one-game deals to make up the road teams all over the league. So it appeared that a team from "Reno" was coming to town, but they were basically a group of guys grabbed from all over to form that night's opponent.
I'm fairly sure that if you showed up at any game site with skates and a helmet, they threw a jersey on you and let you play and slipped you $50 after the game. Lucky Fan, indeed.
The insurance risk must have been significant. The team disappeared one day without a trace. Not a shock.