Bubba Ho-tep (2005)

Based on the short story by acclaimed author Joe R. Lansdale, "Bubba Ho-tep" tells the "true" story of what really did become of Elvis. We find the King as an elderly resident in an East Texas rest home, who switched identities with an Elvis impersonator years before his "death", then missed his chance to switch back. Elvis teams up with Jack, a fellow nursing home resident who thinks that he is actually President John F. Kennedy, and the two valiant old codgers sally forth to battle an evil Egyptian entity who has chosen their long-term care facility as his happy hunting ground.

Official website: http://www.bubbahotep.com/