Crossovers have been kind of a big deal on The CW over the past couple of years thanks to the superhero team-ups between characters from Arrow, The Flash, and the other superhero series. As it turns out, however, The CW almost had a different super crossover a few years before the first time Oliver Queen met Barry Allen. The two long-running series Supernatural and Smallville nearly had a crossover that could have been pretty epic. Former Supernatural writer Jackson Stewart explained the crossover idea, saying this:
There was a lot of really cool ideas that some of the writers had. They had an episode where they really wanted to do a Superman curse that was about every actor who plays Superman ends up getting killed. So they find out that Tom Welling from Smallville is next and have to save him. I thought that was one of the funniest ideas that I'd heard.
Jackson Stewart's contribution to Supernatural was the Season 6 episode "Frontierland," which took Sam and Dean back in time to play cowboy in 1861. The episode was produced in 2011, which coincided with the tenth and final season of Smallville. A crossover featuring Tom Welling rather than Superman while Smallville was still on the air would have seemed impossible...for any show other than Supernatural.
Supernatural is one of the most meta series ever to hit the airwaves. Stars Jared Padalecki and Jensen Ackles have played Sam and Dean who were sent to an alternate reality...in which everybody thought Sam and Dean were actors named Jared Padalecki and Jensen Ackles working on a show called Supernatural. The show's version of God wrote a series of paperback novels about the adventures of Sam and Dean, which would become known as The Winchester Gospel. The 100th episode featured the boys investigating an incident at all all-girls school...which was putting on a musical based on the books about Sam and Dean. Tom Welling turning up as an actor who played Superman while Smallville was still on the air would not be the weirdest thing that Supernatural has ever done, and it probably would have been pretty funny.
Jackson Stewart shared the story of the crossover that never happened in a chat with EW Radio. While it's a shame that we never got the Supernatural/Smallville crossover back in the day, it's not entirely out of the question that we could get a variation of that episode nowadays. Tom Welling still qualifies as an actor who played Superman; he's just been away from the role for a few years. If that couldn't work, perhaps Supernatural could just borrow Brandon Routh from the set of Legends of Tomorrow or Tyler Hoechlin the next time he drops by Supergirl to play the Man of Steel. There haven't really been enough live action Green Arrows or Flashes or Supergirls for Stephen Amell, Grant Gustin, or Melissa Benoist to stand in for Superman, but we can always hope.
Tune in to The CW on Thursdays at 9 p.m. ET to see what's next for the Winchester boys on Supernatural.