Trivia: Data's performance of Henry V was based, in part, on the 1989 film by Kenneth Branagh. In 1980, Patrick Stewart appeared in the TV movie Hamlet, Prince of Denmark with Derek Jacobi, who in turn appeared with Branagh in Henry V.
Trivia: The test objects that O' Brien uses on the malfunctioning transporter are U.S. Navy sonar buoy transport cases.
Trivia: Riker's comment, "Is it just me or does it look a lot meaner this time?" when the Husnock warship appears the second time, is not hyperbole. For that scene, the production crew modified the ship model with a third phaser cannon to subtly appear more menacing.
Booby Trap - S3-E6
Trivia: The Promellian battle cruiser is actually the alien spacecraft from the 1986 horror parody 'Night of the Creeps'. Originally it had been designed with all the detailing on the bottom since it was only filmed from below. The production staff simply turned the model upside down and presto, instant Star Trek ship.
Allegiance - S3-E18
Trivia: In this episode, the stripe on Picard's door is light purple. Usually, the info stripes are brown with white lettering. Also, you see that Picard's quarters are on Deck 9, and has a view of space, whereas Kirk's cabin was further inside, with no windows. This was a means of protecting him from attack.
Trivia: In addition to playing Lt. Worf, Michael Dorn appears very briefly, without makeup, as a tourist on Risa.
The Ensigns of Command - S3-E2
Trivia: Due to a noisy aqueduct on the set, they had to go back and overdub virtually all of the dialogue in the pumping station scenes on the planet's surface. This is most apparent with the character of colony leader Gosheven, who was portrayed by guest actor Grainger Hines. After filming was completed, a schedule conflict prevented Hines from participating in the overdubbing sessions, so another actor rather mechanically voiced Gosheven's lines. The incongruous overdub was so obvious and so unflattering to Grainger Hines that he requested his name be dropped from the episode credits, and so it was.
Answer: Yes. The doors to the holodecks can be locked when in use by anyone aboard the Enterprise so they couldn't be disturbed. However, high ranking officers like Captain Picard could override the doors as it's seen that overrides are in use even for the crews quarters. Even Barclay, when he's indulging in one of his fantasies could have the doors to the holodeck unlocked by an override code.