I just got the Disney Treasures tin of The Adventures Of Oswald The Lucky Rabbit. Inside was a small pin with Oswald on it that looks sort of like an old 20s or 30s design. It was completely unexpected. Have you guys ever bought a dvd set and found an included collectible that you weren't expecting or a feature that wasn't listed on the case ? On the dvd side of things, a few years ago, being a sucker for tv disaster movies, I bought 10.5. When I was watching it, I found a commentary for the movie. It wasn't listed on the cover.

Roughly 2 years ago I bought a used DVD from an Amazon (Amazon UK!) seller, and upon opening the box, discovered the DVD packaging was a steel book! My heart skipped a beat, both because the seller hadn't mentioned this, and knowing how fragile steel books can be. It was in perfect shape! To this day I'm still not sure if all copies were sold this way...Amazon had just the one listing...but it was a great surprise.

I bought "Reign Over Me" based on the good reviews, but unexpectedly, the movie sucked....
I ordered Planet Earth from DeepDiscount, and 2 months later, a second copy came unexpectedly... but they also charged me with it too.
If you want to mention good, there are a lot with hidden easter eggs that are worthwhile.
A random surprise, when I got "Network: 2 Disc Special Edition" there were 2 copies of the jacket cover.
My Artificial Eye Satyajit Ray Apu Trilogy had 2 discs mislabeled and switched....
Criterion Collection had a lot of postcards in their previous releases.
Media Blasters, some other companies include a bonus trailers DVD in their releases.
One of the "Lost" season sets I bought from Amazon came with the Walmart exclusive bonus discs.

Hmmm, I don't know about this...

I bought my brother those Thumb movies (The Godthumb, Bat Thumb, etc.) and there were 2 copies of Bat Thumb in there.

I was surprised by how emotionally affecting Reign Over Me is ...

I REALLY like the idea of calling DVD Easter Eggs 'Unexpected Coolness' instead, but I haven't been surprised by anything such as you mentioned.

Yeah, when I bought Crash Cinema's edition of the kung fu film, MAR'S VILLA, it happened to have two discs in it, one with the English dub and one with the original version, letter-boxed and in Mandarin with English subs. No mention of the second disc on the DVD case. And the subtitled print was a lot better than the dubbed print. A real find, in my book. Great kung fu film, too, by the way.