Mystery Disc is a compilation album by Frank Zappa. It was released on CD in 1998, compiling tracks that were originally released on two separate vinyl records and included in the mail order Old Masters box sets, which were released in three volumes between 1985 and 1987. The CD omits the last two tracks from the 1985 LP, "Why Don'tcha Do Me Right?" and "Big Leg Emma", both of which were included on the CD version of Absolutely Free (1967) in 1989.

The Lost Episodes is a 1996 posthumous album by Frank Zappa which compiles previously unreleased material. Much of the material covered dates from early in his career, and as early as 1958, into the mid-1970s. Zappa had been working on these tracks in the years before his death in 1993.