Action is a member of the Jets in West Side Story.
Action is one of the "Ace men" of the Jets. Like some of the others, his nickname is indicative of his personality; he is very bad-tempered and always ready to fight at the drop of a hat, and as such often needs to be held back by Riff and the others. His irascibility borrows heavily from Tybalt in Shakespeare's Romeo & Juliet, who was also known for his volatile attitude.
Action being 16 by the time of the story, was born January 13th, 1940. Action's childhood was a mix of ups and downs. In 1944, his mother, Mary, married a wealthy man by the name of Jack. Action was living a happy life until he was 8 when his mother contracted a rare form of cancer that was untreatable at the time. His mother passed away 2 years later in 1950.
By 1951, his step-father was gone since he was unwanted and so he ended up living on the streets and moved into an apartment complex where he meet A-Rab and Baby John. Baby John was known as a lighthearted fool by him and he and A-Rab often clashed in A-Rab's Benvolio type additude. The 3 of them wouldn't interact much before meeting Tony and Riff in 1954. They decided to create a gang named the Jets. The 5 of them would go on adventures, defeating other gangs and eventually the gang had more members like Gee-tar, Snowboy and Diesel.
Action was one of several Jets who was against Riff's idea to have Tony stand with him when he challenged Bernardo to a rumble, but Riff, reminding him and the others of how Tony always came through for the gang, proclaimed that Tony would always be a Jet.
After the rumble, during which Riff is killed by Bernardo, Action is boiling with rage and more than ready to get back at the Sharks, but Ice warns him (and the others) that they have to keep from letting their emotions get the better of them.
After Tony is shot dead by Chino, Action, out of respect for Tony, is the first to come forward to pick up Tony's body, along with A-Rab and Tiger, but they're assisted by two members of the Sharks.