Jennifer Garner's opening narration, which was used throughout season one, was literally phoned in. She was working on-location, and had to read it on the phone to J.J. Abrams, who was recording it on the other end.
J.J. Abrams says the idea for the show came from a half-joking story plot for his series Felicity (1998). Abrams considered an episode, where Felicity spends her summer as a government agent, then returns to school the next fall like nothing ever happened.
Greg Grunberg's character was named Eric Weiss. Erich Weiss was the birth name of Harry Houdini. Will Tippin (Bradley Cooper) mentioned this fact when he and Weiss met in season two, episode twenty-two, "The Telling".
While working at A.P.O., the Agents have these following code names: Sydney: "Phoenix", Vaughn: "Shotgun", Dixon: "Outrigger", Marshall: "Merlin", Nadia: "Evergreen", Jack: "Raptor", Rachel: "Oracle", and Thomas: "Sidewinder".
In season five, Rachel Gibson (Rachel Nichols) was created for two specific reasons: 1) Knowing it was the last season, writers wanted to pay tribute to the series by repeating Sydney's first plot (an Agent discovers that she is working for the enemy she believed was fighting) and 2) The show needed a new action character because of Jennifer Garner's pregnancy.
Five different actresses have played Sydney's mother. Arabella Holzbog played Laura Bristow in a picture Sydney kept. Kate Anthony was the voice of Irina Derevko in the video clip shown in season one, episode nineteen, "Snowman". Natasha Pavlovich is the woman we actually see as Irina Derevko in that video clip. April Webster played Irina when she walks up to Sydney at the end of season one, episode twenty-two, "Almost Thirty Years". Finally, Lena Olin played Irina Derevko in the second season and beyond. Additionally, in season four, episode eighteen, "Mirage", Sydney Bristow (Jennifer Garner) briefly portrayed her mother (Laura Bristow) so they can learn information from her father.
After season two, episode thirteen, "Phase One", the show's prominent use of cliffhangers at every episode's end was abandoned for a more traditional (one episode, one story) way of storytelling. This was apparently done, due to demands from ABC executives who were under the impression that new viewers wouldn't "get" the show, and feared a drop in ratings.
The Bank of America tower in Manhattan is used as the exterior shot of the C.I.A. Headquarters in season one. J.J. Abrams later used this building as the exterior of the Boston Federal building on Fringe (2008).
Marshall's (Kevin Weisman's) gadget, the small disc that can knock someone out just by touching skin, he describes it "like freebasing Thorazine". Chlorpromazine (Thorazine) is an anti-psychotic drug, used in the treatment of disorganized and psychotic thinking, and the treatment of false perceptions (hallucinations or delusions.) Drugs of this type are commonly used in mental institutions for patients who do not have a comfortable grasp on reality.
The secret subway tunnel entrance to A.P.O. (seen in the season four premiere) is in the Los Angeles Metro Rail's North Hollywood station, only a few miles from the Walt Disney Studios in Burbank, California.
Director Ken Olin and Writers Jesse Alexander and Jeff Pinkner are the only crew members that directed or wrote episodes in every season. Olin directed twenty-three, Alexander wrote eleven, and Pinker twelve, including the series finale.
The trivia items below may give away important plot points.
Alias had some references to "Alice's Adventures in Wonderland". For instance, in season three, when Sydney returned from her two-year absence, she moved into a new house, since the old one burned down. Eric Weiss (Greg Grunberg) asked her what is the one thing she wishes she hadn't lost (other than Vaughn), she said the first edition of "Alice's Adventures in Wonderland" that her mother gave when she was little. So Weiss gave her a third edition (because he says the first edition cost way too much) to make her feel better. This is interesting, because Sydney was an Alice herself, going deeper and deeper into the rabbit hole. In season one, Sydney dressed up like Alice for Halloween; in season four, Vaughn was directed to "through the looking glass" when he was searching for something in the library, and in season one, Vaughn had a girlfriend named Alice. In season one, episode eighteen, "Masquerade", Sydney's code name was White Rabbit.
The number "47" was used repeatedly throughout the series. Examples: Marshall expressed a desire to improve a camera design, so that it has forty-seven exposures; the key code Will needed to get into a computer room in order to retrieve data on SD-6 is 4747; the crate at the Vatican, which contained the painting with Rambaldi's cipher-key, had a five-digit catalogue number ending in "47"; page 47 was always significant in a Rambaldi manuscript; and of course, there were forty-seven parts to Rambaldi's magnum opus. In episodes of season three, Sydney tried to retrieve memories of when she was abducted, as she was dreaming. Masked men took her into a room with the number "47" largely printed on its doors, and also in the dream, she saw fireworks when she looked through the window, as a reference to the Fourth of July (4/7). Interestingly, the Star Trek television shows also featured the number 47 many times (it's usually seen in their monitors). Also, server 47 was the number of the server that Sydney needed to get information from to take down SD-6.
The Rambaldi prophecy is: "This woman here depicted will possess unseen marks. Signs that she will be the one to bring forth my works. Bind them with fury, a burning anger unless prevented at vulgar cost this woman will render the greatest power unto utter desolation."
Lena Olin was never fired from the show, nor was her character written out as a result of a contract dispute. Olin did not want to rejoin the cast because she lives in Manhattan with her family, and did not want to commute back and forth to Los Angeles for filming. To "cope" with Lena's departure, her character was killed off at the hands of Jack. Afterwards, Lena was available, and Irina was revealed to be alive.