1. It is the second longest running live-action sitcom in history.

Over its 12 seasons, Sons logged an impressive 380 episodes. Ozzie and Harriet holds the title with 425. Want to binge-watch the entire thing? You're going to need some time off. Perhaps a 10-week vacation? (You'll get that joke in a bit.)

2. Eddie Albert turned down the lead role.

The show might have been much different with Albert starring as patriarch Steve Douglas. (The production schedule certainly would have been different, as you will see below.) Albert also passed on playing Wilbur on Mr. Ed, wanting to focus on his film career instead. He would, of course, eventually find a television home on Green Acres.

3. It aired on two networks.

My Three Sons is the rare TV series to enjoy successful runs on two different networks. The first five seasons aired on ABC before the show jumped to CBS. The reason? Colors. ABC was reluctant to cover the cost of producing the show in color.

4. Legendary animal trainer Frank Inn handled Tramp the dog.

The shaggy Tramp had some famous coworkers and friends. The dog was one of Frank Inn's animals. Inn also trained Arnold the pig from Green Acres, the chimps on Lancelot Link, Secret Chimp, and Higgins, the adorable mutt from Petticoat Junction and Benji.

5. There were more than three sons.

"My Three Sons" is a misnomer. There were more sons, and a daughter. Over the course of the show, MacMurray's character Steven Douglas had five children. Mike, Robbie and Chip made up the original triumvirate. The adopted Ernie followed. Then stepdaughter Dodie was added. My Four Sons and Daughter is more apt, though the total number of children on the series is eight, when you count the second threesome of Robert, Steven and Charles — Robbie's triplets. MacMurray must have never heard W.C. Fields' famous quip about childen and animals.

6. Fred MacMurray had plenty of vacation time.

MacMurray worked out a pretty sweet deal for himself. His contract stipulated a cap of 65 days total work per season, with a relaxing 10-week break in the middle.

7. MacMurray's vacations led to continuity errors.

This arrangement caused for some unique (at the time, at least) filming arrangements. The sitcom was shot out of sequence, with production continuing without MacMurray during his vacation. Eagle-eyed viewer will note minor continuity curiousities and frequent scenes with MacMurray away from the rest of the cast.

8. Despite its historic run, the sitcom never cracked the Top 10.

Despite its popularity, My Three Sons interestingly never ranked in the top 10. The closest it came was in season two, when it hit No. 11 on the Nielsen charts.

Image: TV Guide

9. The fifth season drew big audiences.

Despite its lower Nielsen rankings, the show still lured a lot of eyeballs. Season five attracted 13,438,500 viewers during the 1964-65 TV season. There were 52.7 million households with televisions at the time. A quarter of the country ain't bad.

10. The Douglas house was originally a barn in a Gene Autry movie.

The family's home in California was previously featured as the farm in Gene Autry's 1940 musical Melody Ranch. Located on the Republic Pictures backlot, the barn was given a suburban facade in the 1950s. It wasn't that far from Gilligan's lagoon, which was also on the lot.

11. Several characters disappeared with little explanation.

Bub, the grandfather, goes to "visit his mother in Ireland." Mike, the elder brother, is said to have "moved east." Robbie goes to work on a bridge construction in Peru and vanishes in the twelfth season, leaving his young bride and three children with dad. All this led Spy magazine to jokingly speculate in 1987 that Steve Douglas was a serial killer.

12. Lawrence Welk took the theme song into the Billboard charts.

Lawrence Welk's version of the instrumental theme song, written by Frank De Vol, peaked at No. 55 on the Billboard Hot 100 in 1961. Take a listen to the toe-tapping tune.

13. Don Grady played drums in a psychedelic band while on the show.

Billing himself as Luke R. Yoo, the hip actor played drums in the Yellow Balloon. Grady's group even broke into the Top 30, landing at No. 25 on the Billboard Hot 100 the week of May 20, 1967, with its definitive track "Yellow Balloon." The band at one time also featured the drumming of Daryl Dragon, who would go on to become the Captain in Captain & Tennille!