(Reuters) - Pixar movie "Inside Out 2" has crossed the $1 billion mark at the worldwide box office in less than three weeks of release, reaching that level in the fastest time of any animated film in history, Walt Disney Co ( DIS ) said on Sunday.

The film is the highest-grossing movie of the year and the only one to cross $1 billion, said Disney ( DIS ), which owns Pixar.

"Inside Out 2" is a sequel to the 2015 hit about the inner workings of a young girl's mind. In the second instalment, lead character Riley has become a teenager and is grappling with new emotions including anxiety and envy.

The original "Inside Out" opened with about $90 million in its first weekend in the summer of 2015, and topped out at $858.8 million globally.