"Mousemania" is the fifty fifth episode of the lion series of Voltron: Defender of the Universe.
So Pidge tries putting his new cat friends skills to use against the mice. His plan works and the mice are caught in the act. Allura doesn't approve of Pidge's cat chasing her small friends, Pidge however defends his cat by pointing out the mice recent behavior.
That night, Haggar uses her magic to speak with the cat. She orders it to let her cat Cova into the castle. Together, Cova and the Robeast start tearing apart the castle's defensive systems. Eventually both cats are caught by the mice. The mice attack the evil cats with the X-47. The X-47 starts firing its weapons at the cats, who dodge the attacks and damage the X-47.
Before the cats have Cheesy cornered, Cova is about to eat him but Coran arrives. Cova escapes while Haggar transforms the white cat into it's proper Robeast form. The Voltron Force forms Voltron and rushes out into space to rescue Cheesy, who is being held prisoner by Haggar. Pidge manages to rescue Cheesy just as Haggar unleashes the Robeast. The team fights and defeats the Robeast.
Back on Arus, the mice make a cake for Pidge as an apology. Pidge then offers to share the cake with everyone.