It seems a little weird that a show about a bunch of aliens integrating on Earth would focus primarily on something as culturally specific as Valentine’s Day, but that’s what Supergirl did! But the show also used the opportunity to introduce on of Super-canon’s best villains: Mr. Mxyzptlk. But the fifth-dimensional…
Source: Gizmodo – Supergirl Just Had a Super Frigid Surprise Cameo