The Avengers name is commonly used in reference to the popular Marvel comic book characters. In 2012, after previous solo films featuring a few of the group’s characters — Iron Man, Incredible Hulk, Captain America, Thor — the group appeared on screen for the first time. The result was the year’s highest-grossing film ($1.518 billion) and the highest-grossing comic book adaptation of all time, a record that continued to stand in 2015. This led to a 2015 sequel that grossed $1.402 billion worldwide. The Avengers could also reference a popular but unrelated British radio drama/TV series from the 1960s, which was turned into a 1998 feature film.