Can NHL fans really fill in as goalies?

Yes...but they need to be officially declared eligible prior to the start of the game. If you’re attending a hockey game, you don’t have to worry about suddenly being pulled onto the ice.

Here’s an excerpt from the NHL rulebook (link opens a PDF):

"In regular League and Playoff games, if both listed goalkeepers are incapacitated, that team shall be entitled to dress and play any available goalkeeper who is eligible [emphasis added]. This goalkeeper is eligible to sit on the player’s bench, in uniform. In the event that the two regular goalkeepers are injured or incapacitated in quick succession, the third goalkeeper shall be provided with a reasonable amount of time to get dressed, in addition to a two-minute warm-up (except when he enters the game to defend against a penalty shot). If, however, the third goalkeeper is dressed and on the bench when the second goalkeeper becomes incapacitated, the third goalkeeper shall enter the game immediately and no warm-up is permitted."

Additionally, in 2016, the NHL instituted a rule requiring home teams to have local emergency goalie options, both for their own team and for visitors. If enough injuries occur, those amateur players could end up on the ice.

The emergency goalkeeper could be anyone, but teams typically name someone with some goalkeeping experience, since there’s a chance they could get into the game—hockey is, of course, a demanding sport, and occasionally, both a goalkeeper and a backup goalkeeper will suffer injuries.

That happened on Dec. 31, 2016, when Carolina Hurricanes equipment manager Jorge Alves became the first emergency goalie to play in a modern-era NHL game. The 37-year-old former Marine had minor-league experience, but he didn’t face any shots during his brief appearance (he was only on the ice for 7.6 seconds).

“To actually get out there, all of a sudden the lights seemed brighter," he said later. “The lights were brighter out there and it was just like, ‘OK this is crazy.’”

The most famous use of the emergency goalie rule occurred in 2018, when accountant Scott Foster ended up playing for the Chicago Blackhawks. Foster, a 36-year-old from Oak Park, Illinois, had played in rec league hockey, but he certainly didn’t have professional experience.

"Who would have thought? You just keep grinding away in men's league and eventually you get your shot,” he joked to reporters.

Foster came in after backup goalie Collin Delia left the game with 14 minutes left in the third period. The Blackhawks were facing the Winnipeg Jets, who didn’t take it easy on Foster. They put seven shots on goal, and Foster blocked all of them, helping the Blackhawks win the game 6-2.

These instances are exceedingly rare; emergency fill-in goalies usually don’t suit up, apart from the occasional practice. They simply wait in the stands, sometimes receiving petty cash or souvenirs for their “service.”