According to a recently published patent application, engineers at Warner have developed a single DVD disc containing three different laser disc standards. U.S. Patent Application Publication No. 20060179448, entitled "Multilayer dual optical disk," was published last month and includes 22 claims for a multi-format optical disc and "a player for playing an optical disc with multiple data layers." The first claim of the patent claims a disc comprising "a substrate; a first data layer disposed on said substrate, said first data layer conforming to a first protocol; a second data layer supported on said substrate, said second data layer conforming to a second protocol; and a transparent protective layer disposed on top of said first and second layers." Although several formats are disclosed in the application, according to the NewScientistTech article (link below), Warner will be releasing a movie, Lake House, later this month in three different formats on one disc. On one side of the disc, the movie in Blu-ray format will exist (which is read 0.1mm deep) on top of the movie in HD-DVD format, which is read at 0.6mm deep. On the other side of the disc, the movie will exist in standard DVD format. According to the patent application, "as discs with higher capacities are being phased in, content will have to be distributed on as many as three different kinds of discs: standard DVD discs, and two types of high-capacity discs. As noted, this is undesirable for several reasons." (Thanks, Cam, for bringing this to my attention.)

U.S. Patent Application Publication No. 20060179448: LINK
NewScientistTech Article: LINK
CNET News Article: LINK