Up until Snow Leopard, new versions of Mac OS X would play a welcome video during installation. These helped set the stage for the new operating system.
Cheetah, Puma and Jaguar shared a video that highlighted the new Aqua interface. Panther’s featured the bright blue background with nice, crisp, white text. Tiger brought Spotlight, and as such, the welcome message was highlighted by a moving light. Leopard and Snow Leopard shared a darker clip that is reminiscent of the initial Time Machine interface.
I spent a little time digging through disk images to pull them all together into one quick video: