Ryan Reynolds has joined the cast of upcoming live-action Pokemon movie, Detective Pikachu.

The Deadpool star is to play the lead motion-capture role of a Pikachu-type Pokemon with impressive investigative skills, according to The Hollywood Reporter.

The movie is based on the video game Great Detective Pikachu in which players work with Pokemon characters to solve mysteries. Filming will begin mid-January (18) in London.

Ryan joins a cast that includes Paper Towns star Justice Smith, 22, and Big Little Lies actress Kathryn Newton, 20. Goosebumps filmmaker Rob Letterman is to direct.

The film will feature Ryan, 41, as the animated Pokemon detective alongside live-action characters. Early reports have suggested that the plot will begin with the kidnap of Justice's character's father, forcing the teen to pair up with Ryan's Pikachu to investigate his disappearance, with Kathryn tagging along as a journalist who helps them in their search.

Great Detective Pikachu, which was released in February last year (16), is a spin-off of the Pokemon franchise that began in 1995 as a video game in which players had to collect unusual, fictional, animals or Pokemon, train them, and use them in battles.

The game's popularity has spawned a card-collecting craze, an animated TV show, an animated movie franchise, and most recently, the augmented reality game Pokemon Go.

Ryan's role as the anarchic superhero Deadpool in last year's movie won him acclaim for his comic abilities, and a sequel to the blockbuster is scheduled for release in June 2018.

Detective Pikachu is also slated for release next year.