Ronnie, Caitlin wedding in 'The Flash' finale
Ronnie, Caitlin wedding in 'The Flash' finaleScreenshot/Youtube

Packed with time travel and rogue meta-humans, fans have many unrealistic theories about what can be expected in the season finale of "The Flash"; but one thing is certain: "Fast Enough" is going to be tear-jerker.

Grant Gustin, who plays the titular Flash aka Barry Allen, and Danielle Panabaker, who plays Caitlin Snow, have both suggested fans to keep a tissue box nearby while watching the finale episode of "The Flash" on Tuesday, 19 May. While Gustin said, "Next week's finale of @CW_TheFlash is truly heartbreaking." Panabaker tweeted, "Don't miss the Season Finale of @CW_The Flash on Tuesday! And bring some tissues."

Episode 23, which marks the Season 1 finale of The CW series, will see Barry do what he has been mentally preparing himself for since the moment he learned that he can travel back in time: try and save his mother from the Reverse Flash.

In the promo for "Fast Enough", Joe (Jesse L. Martin) tells Barry, "There is no choice here, Barry. You have to do this, you have to change the past." Iris (Candice Patton) is also seen giving Barry a good luck/goodbye kiss before he runs back to 15 year ago as Eddie (Rick Cosnett) looks on happily.

The promo ends with "The Flash" cradling his dying mother's head and revealing his identity, meaning he does travel back to the moment his mother was killed. However, Nora Allen living would alter the universe at large.

In the comic book universe, the event created an alternate time-line, "Flashpoint Paradox" - where heroes become villains and friends turn against each other. If the same scenario is reciprocated in "The Flash", Caitlin and Cisco (Carlos Valdes) can finally assume their villainous identity of Killer Frost and Vibe, respectively.

"From the beginning, I knew that Caitlin Snow becomes Killer Frost. And I can't wait to suit up and duke it out with the boys!" Panabaker said during a Reddit AMA and asked fans to watch out for her transformation in the season finale on Tuesday.

Before turning icy and cold, Caitlin will certainly get married to her love Ronnie (Robbie Amell). In the promo, the two are seen sharing a sweet kiss after exchanging rings.

FIRESTORM, which is part Ronnie and part Dr Stein (Victor Garber), is back to help out friends in STAR Labs in stopping Dr Wells.

Do not miss the Season 1 finale of "The Flash" on Tuesday, 19 May, at 8.00 pm (EST). Watch the promo for "Fast Enough" here: