I once bought a DVD about volcanic eruptions and -- I swear to God -- the content on it was a John Holmes porno entitled Eruption. Everything else (packaging, silkscreen on the disc, etc.) was fine.

I assumed that the same pressing plant was doing *both* of those movies, and got the masters mixed up. Pretty though... and it made for an *ehem* interesting return to the store.

Haven't had this happen with a DVD yet, but years ago I bought David + David's "Boomtown" on CD and, while the disc itself was properly labeled, the music itself was a jazz album I didn't recognize. It wasn't easy getting the record store to take it back -- I had to convince them David + David (who were not well-known then or now) are not jazz musicians. If I remember correctly, I eventually had to show them the lyrics in the CD booklet to prove that the music shouldn't have been instrumental...

I never heard of it happening w/ DVDs, but it does happen with software and CDs.

A lady I worked with bought a CD with nursery rhymes for her kid, ended up getting a Prince album.

I forget what series it was, but there was a math program for 6-7yo kids that actually was a CDROM put out by soft core porno queen Julie Strain.

I bought Butch Cassidy & the Sundance Kid when it was first released. It had one of the discs from a X-Files season set on it.

I bought a DVD with 3 episodes of some old TV show from the 1950's. On the back of the package, the disc itself, and the menu on the screen they list the same 3 episodes, but selecting episode 2 gets you episode 3. And selecting episode 3 from the menu gets you an episode not listed on the package, disc, or menu on the screen!