Roger Rabbit: The Toon Platoon/Who Discovered Roger Rabbit? (cancelled animated film prequels to "Who Framed Roger Rabbit"; late 1980s-late 1990s)

Who Framed Roger Rabbit has had several prequel projects planned, all of which would have been direct-to-video. The idea of a prequel was thought of by the production team as early as the late 1980s, after the original movie's release, but for various reasons, none of them have been fully created.

Roger Rabbit: The Toon Platoon
The first idea for a prequel was Roger Rabbit: The Toon Platoon.

Set during World War II, the story would have involved a young Roger Rabbit rescuing Jessica Rabbit from the Nazis, and the story would have ended with the revelation that Roger’s father is Bugs Bunny.

However, Steven Spielberg decided to discontinue the project after working on Schindler's List, having come to the belief that humorous portrayals of the Nazis would be disrespectful to the victims of the Holocaust.

Who Discovered Roger Rabbit?
In the late 1990s, the idea of a Roger Rabbit prequel was brought back to life, with Steven Spielberg heading it again.

No longer involving the Nazis, this new prequel idea would have been called Who Discovered Roger Rabbit?, and the story now revolved around Roger's rise to stardom on Broadway and in Hollywood. This new project would have had CGI along with the expected live-action mixed with traditional animation. The animation would have been developed by Jim Pentecost, who produced Pocahontas.

Due to a projected budget that was simply too high and "then-current studio politics", this project was also discontinued.

Aftermath
Roger Rabbit CGI Test from 1998.

A 10-second animation "pitch test" from 1998, marked Who Framed Roger Rabbit 2, was leaked online. The short simply featured a prancing Roger Rabbit. It was revealed to have been directed by veteran animator Eric Goldberg, who confirmed the cancellation of the project and specified that the new 3D-animation technique he developed for this test was then later used for the Magic Lamp Theater, a 3D attraction at the Japan-based Tokyo DisneySea. Any other material that could have been produced for either project is unknown.

Additionally, in 2009, there were rumors that a Roger Rabbit sequel was being worked on by Robert Zemeckis, but these rumors haven't been confirmed and nothing has come from them either way.