In 'West Side Story', what are the two rival gangs?

In 'My Fair Lady' (1964), who plays Eliza Doolittle? In 'Singin' in the Rain', who performs the title song dance in the rain? In 'Grease', who plays Sandy? In 'Grease', what is the name of Danny's gang? In 'The Outsiders' (1983), what are the two rival groups? Which 1986 film is about a teenager who skips school with friends Cameron and Sloane? Which 1985 film is about five students serving Saturday detention? In 'Mean Girls' (2004), who plays Cady Heron?