IT’S SUPER CROSSOVER!

An upcoming episode of CBS’ “Supergirl” will feature the crimefighting gal teaming up with CW action hero the Flash. The superheroes — Melissa Benoist as the skirt-wearing wonder and Grant Gustin as the sizzling speedster — both appear on shows produced by Greg

Berlanti and Andrew Kreisberg. The special episode will air on March 28 on CBS. We’re also told that Calista Flock

hart, who plays the boss of Supergirl’s alter ego, was seen on set in Los Angeles filming with the heroic duo.