Short answers, pulled from the story.
Butters transformed into his supervillain alter ego named Professor Chaos and threw a shuriken that became lodged inside his eye. The boys attempted to extract the weapon but failed, so they dressed him like a dog and took him to a veterinarian instead of a hospital.
Trey Parker wrote the episode which originally aired on the 17th of March 2004. This marked the first time April Stewart voiced the bulk of female characters following Eliza Schneider's departure from the show.
Stan Marsh and Kyle Broflovski took Butters to a veterinarian because taking him to a local hospital would have resulted in their parents discovering their purchases from the vendor. They decided to dress Butters up like a dog to avoid parental discovery after an extraction attempt failed completely.
Good Times with Weapons along with thirteen other episodes from South Park's eighth season was released on a three-disc DVD set in the United States on the 29th of August 2006. In 2015, the episode was also included in South Park , The Hits: Volume 1 as one of ten favorite episodes.
Parker performed this song himself during production and delivered lines in both Japanese and English to match the anime parody style. He recorded the theme song called Let's Fighting Love mixed Japanese and English lyrics in a style parody of anime themes including Dragon Ball Z.