Interview:

On Disc 4, go to the second menu of "Post-Production". Highlight "The Final Countdown" and press your Up button once. The second symbol (in a series of five) will light up. Press your Enter button to view an interview with Van Ling on how he first met James Cameron.

Gag:

On Disc 8, go to the second menu of "Post-Production" and highlight "Visual Effects Gallery". Press your Up button and the fourth symbol (in a series of five) will light up. Press your Enter button to view a clip with David Prior playing on one of the Aliens.

All easter eggs were generously submitted by SirDonk