EXCLUSIVE: In a rare instance of working together since 1978’s The Deer Hunter, good friends Christopher Walken and Robert De Niro will go before the cameras next month to take part in a different kind of war: The War With Grandpa, a comedy directed by Tim Hill (Hop). Comedy favorite Eugene Levy who co-starred in the American Pie franchise and pretty much every funny Christopher Guest movie you can think of — also has joined the cast, sources tell Deadline.

Image (4) Eugene-Levy__140211043339-275x403.jpg for post 680879

The War With Grandpa, based on the book by Robert Kimmel Smith, is about a kid who reluctantly gives up his bedroom to accommodate his grandfather (De Niro), whom he loves but wants out of his room. The boy engages in a series of pranks meant to drive his grandpa out, but the old man is pretty wise to it and returns the volleys. De Niro and Walken play best friends in the film — as they did Deer Hunter, won the Best Picture Oscar and earned a Supporting Actor statuette for Walken.

The comedy is being produced by Marro Films and distributed by Dimension. Matt Ember and Tom Astle, the team behind the DreamWorks Animation hit Home and MGM’s Kid Robot did a rewrite; Lisa Addario and Joe Syracuse also get credit for the screenplay. De Niro began negotiating for the film this summer.

The War With Grandpa is being produced by Phillip Glasser, Marvin Peart and Rosa Morris-Peart, and Jane Rosenthal and Berry Welsh are the exec producers. TWC’s Dimension opens the film April 21.

Walken — who, like De Niro, has had a long and successful career in both drama and comedy — is repped by ICM Partners. Levy is repped by ICM Partners and additionally repped by Great North Artists Management and Anonymous Content. De Niro is with CAA.