Kryptonite Dog
From superman.nu: Supermanica
The evil pet of the Kryptonite Kid who shares the power of Green Kryptonite and is the sworn enemy of Krypto.
In September 1960 the Kryptonite Kid and his Dog pass through a green cloud in space, both gaining an emerald hue and the attributes of Kryptonite, deadly to Superboy and all survivors of Krypton. The duo journey to Earth and use their Midas-like ability to transform everyday objects into Kryptonite, threatening the lives of Superboy and Krypto--who are only saved at the last minute by the 5th-Dimensional magic of Master Mxyzptlk (SB No. 83/1: "The Dreams of Doom").