Dot Matrix is one of the major characters in Mel Brooks' Spaceballs. She is a female parody of C-3PO and voiced by the late Joan Rivers.
As Princess Vespa prepares to reluctantly marry the lethargic (hence his name) Prince Valium, Dot Matrix (who is named after a printing style) attends the wedding as Vespa's "Droid of Honor." Vespa un-shockingly gets cold feet and storms off in her luxury starship. Dot gets literally dragged along for the ride.
Dark Helmet sees Vespa and Dot in range and, realizing the princess would be the perfect pawn in acquiring more air for Planet Spaceball, proceeds to kidnap her. Her father, King Roland, proceeds to make an offer with Lone Starr and Barf to rescue her for 1,000,000 spacebucks.
Once Lone Starr gets in position, he and Barf jam Spaceball I's radar with a giant jar of raspberry jam, then Barf helps Vespa and Dot board their ship, the Eagle 5. Fighting ensues within Starr's ship with Lone Starr poking fun about how she's a Druish Princess (a play on the archetype Jewish Princess) and Vespa playing that stereotype perfectly. They then enter Hyperactive (parody of Star Wars' Hyperspace) with Dark Helmet using "Ludicrous Speed" in an attempt to catch up.
The Eagle 5 crash-lands on the Moon of Vega, leaving Lone Starr, Barf, Vespa, and Dot Matrix to try and survive the harsh desert land. Vespa, in her Druish Princess self, makes the men carry a ridiculous amount of luggage, which they soon drop in the sand. Lone Starr and Vespa fall in love, but Dot's "Virgin Alarm" goes off before they can share a kiss. The following night, Dark Helmet tracks Vespa down to Yogurt's lair, and tries to lure her into his grasp by disguising as her father. Dot sees through the ruse with her "Super Vision", but fails to warn Vespa in time. Consequently, they both get kidnapped, until Lone Starr and Barf travel to Planet Spaceball and rescue them.
After Lone Starr saves Druidia from the Spaceballs, defeats Dark Helmet, and finds out he's a prince, he and Vespa decide to marry each other. Dot attends their wedding as Vespa's Droid of Honor. As she watches the couple kiss, she delivers the last spoken line of the movie: "Well, goodbye, Virgin Alarm."