The flash finale
Barry, Felicity and Ray Palmer in The Flash episode 18 The CW

A new trailer for The Flash finale was released at the 2015 WonderCon held at Anaheim Convention Center on 5 April.

The trailer teases a kiss between Barry and Caitlin Snow, the arrival of Felicity and Ray Palmer in Central City, as well as Harrison Wells aka Reverse Flash's end-game.

Here are a few things we know from the WonderCon 2015 panel discussion.

Barry saving his mother might create an alternate timeline, called the Flashpoint.

"Time is an extremely fragile construct how many more people could die if your mother lives," says Harrison Wells in the trailer video.

Executive producer Andrew Kreisberg hinted at seeing the ramifications of an alternate timeline where Barry's mother survived, which would likely be the Flashpoint Universe.

Speaking at the Wondercon panel this weekend, Kreisberg said that there's a very big difference in the timeline that will affect the characters. "In the final few episodes, the characters will hear about their future and where they should have been/will go. We will see everyone's reaction to that knowledge and how the characters decide to act on it to alter their own futures."

The promo video also shows a kiss between the Speedster and Dr Caitlin Snow, which is shocking for various reasons.

While Allen is in love with Iris, the last we checked the doctor still had feelings for her fiancé Ronnie, aka the Firestorm.

Caitlin Snow teases becoming the Killer Frost, a classic villain

When asked about the possibility of becoming the villain, Panabaker teased "You're going to see her sooner than you think." Whether that will be some sort of alternate timeline tomfoolery or whether Snow will go full villain remains to be seen.

Felicity and Atom in Central City

The Flash's all new episode will feature Barry and Ray Palmer fighting alongside.

Episode 18 is titled, All Star Team Up, where Barry will tell his Star Labs team-mate that Harrison is the Reverse Flash who killed his mother.

The official synopsis reads as follows:

Barry (Grant Gustin) is surprised when Felicity Smoak (guest star Emily Bett Rickards) arrives from Starling City along with her boyfriend, Ray Palmer (guest star Brandon Routh), who flies in as the Atom. They've come to visit S.T.A.R. Labs as Ray needs help with his suit. Their timing turns out to be fortuitous because it's all hands on deck after a meta human named Brie Larvin (guest star Emily Kinney) unleashes hundreds of robotic bees to attack and kill her former co-workers, including Dr. Tina McGee (guest star Amanda Pays). A group dinner with Barry, Felicity, Ray, Iris (Candice Patton) and Eddie (Rick Cosnett) turns into a disaster.

Here are a few questions from the WonderCon 2015 Trailer:

What are Barry, Cisco and Caitlin doing in Dr Wells's secret "future" room?

Will Gorilla Grodd Kill Joe West?

Why is The Reverse Flash trapped behind bars?

Is Eddie Thawne evil?

Just as the time travel bandit says in the trailer, "The real end-game is almost here. This is going to be fun."

Gear up for the fun and shock of the last six episodes ahead.

More about The Flash