It was probably inevitable.

Fan Expo got underway at the Metro Toronto Convention Centre Thursday, and with it came an array of excited, costumed fans.

One of those fans apparently startled some GO transit passengers this morning: Toronto police got a call at about 10 a.m. with reports of a person with a gun. It turned out to be part of someone's outfit.

"As with any type of call like this we treat it as a real threat, and then we work our way back down to ensure that there's no threat," Const. Victor Kwong told CBC News. 

"In this case we were not able to find anyone and in fact speaking to many people it appears as though it might be tied in with Fan Expo."

fan expo union gun call

Police officers waiting on the platform at Union Station after receiving calls about a person with a gun. (Matt Llewellyn/CBC)

Kwong says that riders should be aware that the event runs throughout the weekend, and more costumed passengers may be sharing their train cars. 

"You will see people dressed as their favourite characters, and some of those costumes will have, shall we say, accoutrements, whether it be weapons or things like that."

But Kwong also wants to reassure people they shouldn't hesitate to call police if they see anything concerning. In fact, due to the many special events this weekend, GO transit will have additional security on hand.

Metrolinx spokesperson Alex Burke told CBC News that it's all in good fun, but anyone in costume should be aware of their fellow passengers. 

"We love a good Fan Expo costume but we are encouraging those attending to respect that other passengers may not be able to distinguish what's cosplay [and] what's reality," she said. 

"While we don't want anyone leaving their phasers or whatnot at home, maybe consider keeping more realistic accessories stored until you arrive at your destination."