Supergirl is pretty good when it comes to dealing with supervillains that can shoot lightning or blast kryptonite out of their chest, but Kara might have here hands full with Mr. Mxyzptlk. An interdimensional being with a name that's a pain in the ass to type and the powers to basically do anything, he's got his sights set on Kara, and not in a super great way. She's become the object of his crazy affections and in order to give him a real shot, the producers decided to update his costume from "small cartoon man in orange" to "CW handsome."
Peter Gadiot (Once Upon a Time in Wonderland) was cast to play Mxyzptlk in an upcoming episode of Supergirl that will find the character trying to win the heart of Kara through his reality-bending powers. His comic book appearance isn't easily translated to screen and was in need of a major update. Gadiot told TVLine that the character looks different to better sell the romantic angle of the episode.
I don't really see Kara running off with a random guy from the 5th dimension as an actual possibility -- no matter how handsome he is -- but I guess you have to find the drama somewhere. Mxyzptlk showing up just as Kara and Mon-El are about to kiss definitely points a wrinkle in their budding romance, and his reality-bending powers don't exactly make him easy to get rid of.
Here's a photo of Mxyzptlk as he is in the comics so everyone can see why he needed that CW facelift.
Mxyzptlk is somewhat of an obscure character so here's the rundown: he's a magical imp from the 5th dimension who routinely shows up to mess with Superman. He has the powers to bend reality, which means that he can literally do anything; he can conjure things out of mid-air or he could turn everyone on earth into a duck if he wanted to. Usually, the only way to get rid of him is to trick him into saying his name backward, but it's possible Supergirl won't go down that route and will come up with something else.
You can catch Peter Gadiot as Mr. Mxyzptlk this week when Supergirl airs on Monday 8 p.m. EST on the CW.