ComicBook.com has revealed that the Imp from the 5th Dimension Mr. Mxyzptlk will be making his début on Supergirl for a two episode arc, in which Mr. Mxyzptlk attempts to make Supergirl his bride. No actor as been announced, but he will be younger than normally seen.
— Comicbook.com (@ComicBook) December 2, 2016
While Mr. Mxyzptlk is known for being a villain of Superman, he has had an arc for Supergirl titled “Cosmic Adventures in the Eighth Grade” in which Mr. Mxyzptlk was responsible for Supergirl’s arrival in Metropolis and goes in disguise as a principal at Supergirl and Lena Luthor’s school.
Mr. Mxyzptlk has appeared on live action TV in past with Oscar Winner Michael J. Pollard (Superboy), Howie Mandel (Lois & Clark: The New Adventures of Superman) and Trent Ford (Smallville) all playing the role in different ways.
In animated Gilbert Gottfried is the most known for voicing the role in Superman: The Animated Series. But Frank Welker (Super Friends) and Gilbert Mack (New Adventures of Superman) also voiced him earlier on.
Mr. Mxyzptlk is a perfect example of what the Silver Age did that worked really well and as we have seen from the Berlanti shows the Silver Age is very much a huge inspiration.