At Fred MacMurray's insistence, all episodes were filmed out of sequence during the show's entire run using a technique now known as the MacMurray method. MacMurray would do all of his scenes in 65 nonconsecutive days. The cast regulars got haircuts once a week in order to maintain continuity. Guest stars would have to return months later to complete an episode. All kitchen scenes would be done together, then all scenes in the upstairs hallway would be filmed together, etc. This fact was well concealed until Dawn Lyn joined the cast as Dodie. Her upper front teeth grew in irregularly during the entire 1969-70 season, from being barely visible in scenes with MacMurray to being plainly visible in scenes without him. William Frawley never felt comfortable with this method of filming, having grown accustomed to filming "I Love Lucy" in sequence during its entire run.

William Frawley really enjoyed working on the show and did not want to leave. To make matters worse, he was replaced by William Demarest, whom he hated in real life.

Don Grady almost left the show when Tina Cole was cast as Katie. In an interview, Cole revealed that Grady felt she wasn't his type. As it turned out, they eventually fell in love in real life and almost got married not once, but twice.

The show moved to CBS after ABC refused to finance the higher cost of filming in color.

The show was originally going to be named "The Fred MacMurray Show," but Fred MacMurray didn't like the idea.

Not only was the first episode of the 1965-1966 season the series' CBS debut, it also was the first episode to be shot in color. Before taking the role of Katie, Tina Cole appeared on a couple of earlier episodes in various roles, always being cast as one of Robbie's girlfriends.

When Don Grady left the show in the final season, his absence was explained by having Robbie get transferred to Peru by his job and have Katie join him there.

The character Steve Douglas is an Aeronautical Engineer specializing in Structural Design. He is also a former Test Pilot.

Although officially leaving after the show's fifth season in 1964-1965, Tim Considine's last appearance as Mike, the eldest son, was actually in the first episode of season 6 (the series' first in color). The episode opened with a brief scene showing Mike and Sally's (Meredith MacRae) wedding. The episode also "launched" Barry Livingston ("Ernie") as the new son. The characters of Mike and Sally were mentioned in the next two episodes, which dealt with Ernie's adoption, and in a subsequent episode when Charley and the boys thought Steve was getting married. Mike was referred to by name one last time in the second 1966-1967 episode, when the gang visited Steve's hometown. After this they were never referred to by name again for the remainder of the series, although Mike was indirectly referred to as, "the first of you" by Steve a few years later.

The name of the town where the Douglasses lived before moving to California was Bryant Park. However, the state the town was in was never named.

The character 'Steve Douglas' was ranked #7 in TV Guide's list of the "50 Greatest TV Dads of All Time" (20 June 2004 issue).

Tim Considine and Meredith MacRae dated in real life while they were on the show while Don Grady and Tina Cole almost got married in real life. They broke up shortly before Grady left the show.

When Barry Livingston first joined the show as Ernie, he replaced the character of Sudsy Pfeiffer as Chip's best friend. At that time, despite their noticeable age difference, both boys were in the same grade. However, once the character of Ernie was added as a regular to the series, he reverted to his actual age, three years younger than Chip, effectively establishing him as Chip's kid brother.

June Haver, Fred MacMurray's real-life wife, recommended Beverly Garland for the role of Barbara.

With 369 episodes over 12 years, this is the second longest-running (live action) comedy in US TV history (as of February 2003), surpassed only by The Adventures of Ozzie and Harriet (1952).

In the first years 1960 - 1964 Chevrolet was the sponsor and different models were shown throughout each show. Steve Douglas had a 1961 Impala station wagon for the first year. The ending credits also showed Chevrolet photographs which were used in the print ads of the time. In 1964 - 1970 Pontiac was the most noted car sponsor, where Steve had various blue Pontiac Bonneville station wagons while Robbie drove a 1954 Pontiac Star Chief convertible, occasionally nicknamed the "old coffee grinder" by his classmates. In 1970 - 1972, Ford Lincoln Mercury was the sponsor, and Steve had a Mercury Marquis station wagon.

Fred MacMurray renewed his contract annually during the show's entire run.

One of the very few television shows to survive a change in networks. At the beginning of the 1965-1966 season, the show moved from ABC to CBS, where it ran for its final seven seasons.

When William Frawley left the show midway through the 1964-65 season due to declining health, his absence was explained by having Bub move to Ireland to live. He was referred to several times in subsequent episodes that season, then was never mentioned again once the show moved to CBS.

According to one account, Chip was born Richard but as a toddler pronounced his name Chipper. The name stuck and as he got older it was shortened to Chip. If you'll notice his dad regularly called him Chipper.

The house on the first few seasons was in fictional "Bryant Park". This house is a real residence located at 838 5th Avenue in Los Angeles, California.

The first seven seasons were filmed at Desilu Studios. The sale of Desilu to Paramount prompted filming of the series being shifted to CBS Studio City. The move largely necessitated the relocation of the family to California.

William Frawley left the show because of his health; the studio could no longer get insurance on him. Frawley passed away, at age 79, about a year after leaving.

Don Grady has said in interviews that William Demarest was like William Frawley after an AA meeting. Both were curmudgeons, but Frawley was much jokier and a lot funnier, whereas Demarest was just a grouch (much like his character). Apparently, the two were not fans of each other, either; they were longtime showbiz rivals. According to cast members, the day Bub was being shipped off to Ireland and Uncle Charley was moving in to take up housekeeping duties, the tension between the actors was palpable.

When the character of Ernie was officially adopted by the Douglas family, his dog, Wilson, disappeared without explanation.

The exterior set used for the outside of the main house in the film was actually the barn from "Melody Ranch (1940)" with added features.

One of the original choices for the role of Steve Douglas was Eddie Albert.

Several years later it was revealed that there were different plans in the works for the character of Robbie when Don Grady left the show. One plan was for Robbie and Katie to divorce and another plan was to have Robbie killed off.

Uncle Charley served in the Merchant Marines before coming to live with Steve and the boys.

Chip is the only son to stay for the entire series. However, he's absent during a lot of season 12, only appearing in 8 episodes. Other earlier episodes he's missing from are The Love God and The Recital.

Charley was Bub's brother.

Even though Don Grady left the series after Season 11, his name remained in the opening credits in the 12th and final season.

As of 2018, Barry Livingston is the only surviving regular cast member active in the Screen Actors Guild.

None of the cast members who joined the show in the color era lasted 100 episodes or more.

Fred MacMurray was the only cast member to appear in all three hundred eighty episodes of the series (or in other words he was always 'edited-in' after the episode was completed). Stanley Livingston did stay for the whole 12-season run, but was absent for three episodes.

The shaggy dog on the show was trained by Frank Inn. The dog's name was Tramp.

This show was in the same television "universe" as "Family Affair (1966)" and "To Rome with Love (1969)" due to the fact that all three shows were produced by the same company. In fact, Robbie and Katie made a crossover appearance on To Rome with Love. Interestingly, there were no crossovers between My Three Sons and Family Affair.

The theme song is reminiscent of a family band. The rhythm part is Chopsticks, as would be played by a kid, with the other backing instruments being played at increasingly higher skill levels by age. The lead melody on saxophone, which is played very well, would represent the father, played by Fred MacMurray. During the sixth season, McMurray starred in the popular Boy Scout film Follow Me, Boys! (1966), in which he was a saxophone player who ends up in a small town, becomes a Scoutmaster, and becomes a guiding light for boys.

After William Frawley and Tim Consindine left the show, Bub and Mike were largely forgotten. No mention was made of Bub, and Mike was only indirectly referenced on a few occasions. Similarly, Ernie's having been adopted by the Douglas family was never mentioned as the show progressed.

Several episodes of the later series The Brady Bunch contained "recycled" plots from this show: Katchoo (1969), was from Tramp or Ernie (1966). The Winner (1971) was from A Hunk of Hardware (1966). And Two Petes in a Pod (1974) was from The Wrong Robbie (1966).

The Douglas's often seen Dutch Colonial style "California house", with its familiar stone exterior walls and Gambrel roof, can also be seen in Season 2 of "Leave It To Beaver". It also made an appearance in "Panic in Year Zero" (1962), with Ray Milland. The exterior can be seen at the beginning of the movie. This same house exterior can be also seen in "Melody Ranch" (1940) in a slightly different earlier design.

Interestingly, Doris Singleton appeared on the show playing both Mike's and Chip's mother-in-law. During the fifth season, Singleton played Sally's mom Helen as Sally and Mike were preparing for their wedding. She would later appear in season 11 playing Polly's mom Margaret during in the run up to Chip and Polly's elopement.

Ronne Troup, who played Chip's wife Polly, was supposed to be 18 when she was introduced. In actuality she was 25 when she first appeared on the show.

During later seasons, the exterior of the aircraft plant Steve, and for a while Robbie, worked was actually the Hollywood Burbank Airport, aka Bob Hope Airport.

Ernie's adoption is briefly mentioned in the season ten episode "Dodie's Dilema." When the family is gathered around the kitchen table following Dodie's adoption, Ernie tells Dodie, almost in passing, thats he's also adopted. This is the first time Ernie's adoption is mentioned in the five years since he joined the family. Surprisingly, Dodie doesn't seem surprised by the news, and there's no followup dialogue about his adoption.

The Closed Captions describes the show's theme music as "swanky orchestral music" and the opening scene theme as "jaunty woodwind music."

Throughout its 12 season run, there was only one Thanksgiving episode and no Christmas episodes.

This can be seen as a precursor to "The Brady Bunch."

Steve tells the story that Bub got his name because Chip mispronounced the name "Bill".

Tina Cole's real life father was Buddy Cole, an accomplished pianist and organist. used in the TV entertainment world and on LP vinyl records.