'The Flash' season 3 spoilers: Four-way DC crossover 'Supergirl', 'Arrow' and 'Legends of Tomorrow' teased in new image

The Flash - crossover with Legends of Tomorrow, Supergirl and ArrowTwitter via Stephen Amell

With "Supergirl" season 2 now airing on The CW Network instead of CBS, the doors have been opened for a massive crossover uniting "Supergirl," "The Flash" season 3, "Arrow" season 5 and "Legends of Tomorrow" season 2. In light of this upcoming crossover event, actor Stephen Amell has shared the first teaser image. 

Amell, who plays Oliver Queen aka Green Arrow, recently shared an image via Twitter that focuses on only the feet of several characters but they are still quite recognizable. In the image are Green Arrow, Sara Lance (Caity Lotz), the Atom (Brandon Routh), Supergirl (Melissa Benoist) and the Flash (Grant Gustin), hinting they are all together filming the crossover episodes.

Crossovers have occurred before but only in small doses. It was normally the Flash appearing in "Arrow" for one episode and then Green Arrow appearing for an episode in "The Flash." Flash also had one appearance on "Supergirl" season 1. This will be the first time that all four shows combine for a massive crossover event.

Speaking to Entertainment Weekly, producer Greg Berlanti explained that in order to get this done the heroes would be facing one big threat, "I'm going to probably try to have one unifying threat, as opposed to different things on different ones, which is what the first year was."

Screen Rant reports that "Legends of Tomorrow" season 2 will be introducing both the Legion of Doom and the Justice Society of America. The former is a group of villains comprising of Captain Cold (Wentworth Miller) and Malcolm Merlyn (John Barrowman) among others. The Justice Society is an alternate version of the Justice League on different realities such as Earth-2 or Earth-3.

It is hinted that the Legion of Doom would be the unifying threat that puts the four groups of heroes together although this is still based on pure speculation and must be taken with a grain of salt.

"The Flash" season 3 premieres this Oct. 4 followed by "Arrow" season 5 on Oct. 5. "Supergirl" season 2 premieres Oct. 10 and "Legends of Tomorrow" season 2 will premiere on Oct. 13.