A bloodhound anti-jive reformer, full name: Mr. I.M. Square, from Delaware. He comes to combat swing music jitterbugs, having successfully campaigned against the Fox Trot. He's a regular in the short-lived swing music-themed teenage funny animal comic book Hi-Jinx. He immediately comes to love swing music, despite remaining a square.
He enters the Big Croon and Swoon Contest in the "Square and Warmer" story of #2 (September-October 1947). The winner is whoever makes the most girls swoon. He can sing, but only in the bath, so has to perform in a tub. This gag was reused in "The Flintstone Canaries" episode (10/24/1964) of animated television series The Flintstones.
His name is a reference to the song "You're a Square from Delaware" by Fats Waller.