Watch the full length trailer for Arrow/Flash crossover episode

DC fans will be pleased to see an extended trailer has arrived for the Arrow and The Flash crossover episode, which will definitively introduce the heroes of Legends of Tomorrow. No matter which show you watch, you're going to want to check this out...

The two-part crossover, starring Steven Amell as Arrow and Grant Guston as The Flash, will air in December. Basically, the first part - titled Legends of Today - is Flash's episode, with the second focusing on Arrow, which is called Legends of Yesterday.

It's all building up to a 16-part spin-off series - Legends of Tomorrow - which kicks off in January. Throughout both episodes and the new series, we'll be seeing plenty of other DC Universe characters, such as Hawkgirl and Hawkman (who are obviously not to be mixed up with Marvel's Hawkeye), which will be a massive step forward in DC's plans for an expanded universe.

Legends of Today and Legends of Yesterday will air on December 1 and 2, with Legends of Tomorrow starting in January 2016.