According to The Hollywood Reporter, John will write, produce, direct and star in the new project, titled "Imaginary Friends", for Paramount Pictures.
Ryan will co-star as a Doctor Dolittle-like character who can see and talk to people's imagined pals, befriending those that have been forgotten as kids grow up. His character will have to save the world from those who turn evil due to the loss of companionship.
The mooted new movie is the second comedy Ryan has entering development, as he is also set to star in a comic musical interpretation of Charles Dickens' "A Christmas Carol" alongside Will Ferrell.
Paramount chiefs reportedly landed "Imaginary Friends" after a fierce bidding war with other studios.
The Office U.S. star John is in high demand in Hollywood following the success of his hit horror film "A Quiet Place", which he directed and starred in alongside his wife Emily Blunt. A sequel is currently in the works and will be released next March (2020).