Stephen Amell teases 'Arrow,' 'Flash,' 'Supergirl,' 'Legends' crossover on Twitter

LOS ANGELES, Aug. 8 (UPI) -- Stephen Amell has taken to social media to tease an upcoming crossover special between superhero series' Arrow, Flash, Supergirl and Legends of Tomorrow.

The actor who portrays main protagonist Oliver Queen aka Green Arrow on Arrow, hinted that production had perhaps started on the crossover with an uncaptioned image on Twitter Sunday that featured the footwear of various heroes across the CW's DC Comics television universe.

The photo features the legs of Green Arrow (Amell), The Flash (Grant Gustin), Supergirl (Melissa Benoist), White Canary (Caity Lotz), and The Atom (Brandon Routh) standing around in a circle.

Announced back in May, the crossover special, due in December, is set to take place over four episodes, one for each series.

"Just imagine what our superhero crossover episode is going to look like come December," CW President Mark Pedowitz noted previously.

The CW's DC Comics television universe will resume with new episodes starting with the Season 3 Premiere of The Flash starting Oct.4.