Sir Patrick Stewart is a consummate actor whose professionalism is beyond reproach.... except when Sir Patrick Stewart isn't, because Sir Patrick Stewart can't remember his damn lines. As you might guess, this blooper reel — more of which will be on the Star Trek: TNG season 4 set released tomorrow — features the latter.
Additional warning: Once you see Worf giggle, you can never unsee it. From one who knows.
[Via The Mary Sue]