Back in April of last year, we brought you the report about Robert Downey Jr. (Untitled Sherlock Holmes Sequel, The Avengers) signing on to take the lead role in Walt Disney Pictures‘ Wizard Of Oz prequel, Oz: The Great And Powerful. In October, Disney has hired Pulitzer Prize-winning playwright David Lindsay-Abaire to rewrite the script, and director Sam Raimi (Drag Me to Hell) signed on to helm the project.

Now, THR reports that Robert Downey Jr. has bailed out on Oz: The Great and Powerful, and the studio is in discussions with Johnny Depp (Rango, Dark Shadows) to take over the lead role of Oz, a young illusionist with a grandiose attitude who is forced to flee a traveling circus. His hot air balloon is swept up by a tornado to the land of Oz, which is run by two magical wicked witches.

In other Robert Downey Jr. news…

The actor will soon jump into the WABAC Machine. EW reports that Robert Downey Jr. has signed on to star in DreamWorks Animation‘s forthcoming CG Animated film, Mr. Peabody & Sherman, voicing the floppy eared, bespectacled canine Mr. Peabody, who uses The WABAC Machine (pronounced Wayback ) to travel through time. The machine was constructed by Mr. Peabody as a birthday gift for his “pet boy” Sherman, so that they could visit famous historical events.

Mister Peabody and his pet boy Sherman appeared in a cartoon segment entitled “Peabody’s Improbable History”, which was an ongoing feature of the 1960’s cartoon series The Rocky and Bullwinkle Show.

Peabody’s Improbable History – Robin Hood

Oz: The Great and Powerful is slated to hit theaters in 2013.

Mr. Peabody & Sherman is slated to hit theaters in 2012.