In Meet the Wario Bros., Wario's original sidekick was a cat he had just named simply, Sidekick. His Sidekick is a cat who actully never helps Wario. The cat that is now Wario's sidekick used be Bowser Jr. Usally Wario will work with Bowser. We never see Wario's sidekick. Later on in Meet the Wario Brothers, we see Wario's sidekick changes to Waluigi, but since Waluigi got killed by Mario and Luigi, we can only asume Wario's sidekick is back to the little kitty cat.