Rush in Rio Easter Egg - Anthem 1975

Put in disc 2 of the Rush in Rio DVD
Select O Baterista. You can view the entire clip or return to the menu after it starts.
When you return to the menu, select YYZ
Upon returning to the menu, select YYZ again
After that, select O Baterista
When you return to the menu, Anthem 1975 will appear and you'll be able to watch a video of Rush playing Anthem from back in 1975.

Reason for this: O Baterista is video clip #2, and YYZ is clip #1. Viewing them in the order above, you get 2112.