“That’s really cool.

I had no idea.”

Grant Gustin’s final crossover happened without his knowledge.

The Flash – “A New World, Part One” – Image Number: FAL910fg_0018r – Pictured: Grant Gustin as The Flash – Photo: The CW – © 2023 The CW Network, LLC. All Rights Reserved.

Grant Gustin on ‘The Flash’.The CW

The Flashstar appeared in theApril 20th episode ofTitans, titled “Dude, Where’s My Gar?

The actor laughs as his cameo in that scene is explained to him.

“This is good.

Don’t cut this,” Grant says, adding, “It’s old footage, obviously.

That’s really cool.

I had no idea.”

Gustin previously thoughtStephen Amell’s final appearance as Oliver Queen a.k.a.

the Green Arrowin the final season ofThe Flashwas going to be his last crossover moment.

“And we also just had so much fun.

It was exciting to have Stephen back.”

The Flashseries finale airs Wednesday, May 24, at 8 p.m. ET/PT on the CW.