Supernatural Season 12 spoilers, release date: Supernatural to cross over with The Flash? Cas to go on a mission against Lucifer in upcoming season

Are the Winchester boys set to cross over to The Flash universe? This was the question on fans' minds when Jensen Ackles tweeted a video of himself and his co-star Jared Padalecki snoozing on the set of The Flash. Both shows are aired by the CW.

In his tweet, Ackles poked fun at Flash lead star Grant Gustin and asked him how he got any work done on set when there were too many rules.

Rumors of a crossover should not be completely ruled out as CW shows have been known to feature guest characters from other shows. As a matter of fact, the network is planning a four way crossover, its biggest event for the upcoming seasons of Arrow, The Flash, Legends of Tomorrow and new kid on the block, Supergirl.

It remains to be seen if Supernatural will play into the fore, or how the Winchesters' universe will play into the world of DC heroes.

Meanwhile, a report by Hall of Fame hints that the Men of Letters will become an even bigger threat to the Winchesters in the upcoming twelfth season.

It can be recalled that last season, Sam was injured and kidnapped by members of the organization. Dean is expected to catch up to them and rescue his brother in the early episodes possibly with the help of his mother, Mary Winchester, who was also a hunter.

While the reunion is expected to result in some awkwardness, the boys are no stranger to family drama so they are bound to take the distrust and uncertainty in stride.

Meanwhile, Cas, after becoming Lucifer's vessel for some time in the previous season, will return to his former determined and driven angel persona and will be going after Lucifer full throttle.

"Cas comes out swinging in the beginning of the season and he's a man on a mission, trying to hunt down Lucifer," Misha Collins, who plays Cas, told Buddy TV.

The 12th season of Supernatural is set to air on The CW on October 13.