From the disc's main menu, go to the chapter menu, and use the 'Down' arrow key on your remote control to scan through chapters 1-4 in successive order. Use the 'Right' arrow key to immediately move from chapter 4 to chapter 8, then press 'Right' again. This will highlight in yellow '8 1/2 - Hidden Chapter'. Press Play, and it will play an outtake segment in which Leonard Nimoy discusses one of the early jobs he had while as a struggling actor, working in a pet store as a 'fish doctor', while William Shatner discusses scuba diving and the erosion of coral reefs.
Another hidden feature is located in the 'Biographies' section on the disc. Highlight the 'Creative Media' slogan, which will take you to an overview of Creative Media Entertainment. Press the 'Right' arrow on your remote control, and it will highlight the Creative Media logo. Now press 'your Enter button', and it will highlight a still photograph taken on the set of "Star Trek" from the 1960's with Shatner and Nimoy in what appears to be the buff!
All easter eggs were generously submitted by SirDonk