“Come and knock on my door” wasn’t the original opening for Three’s Company, the 1970s hit sitcom adaptation for ABC.

Nope. Try “doo-dee-doo-dee-doo-dooo” instead. The first taped pilot for Three’s Company didn’t have the lyrics you came to know and love yet from Don Nicholl and Joe Raposo. John Ritter was the star, but his name was “David” and not “Jack Tripper.” The Ropers were there (Audra Lindley and Norman Fell) as the landlords. But Ritter’s roommates were originally played by Valerie Curtin, cousin of Jane Curtin and then-spouse of Barry Levinson, and Suzanne Zenor.

As written and developed by Larry Gelbart, “David” was a film student in Hollywood who used to be a cook, and not an aspiring chef/restauranteur. His would-be roommates were “Jenny” (Curtin), who worked at the DMV, and “Samantha” (Zenor), a model and actress. It opens with the women hungover after a wedding party which found their third roommate getting married, having a baby and leaving all offscreen and only mentioned in dialogue.

They’re in Hollywood, not San Diego — the apartments look the same, though;’ the jokes, too. Including the now-classic thematic plot device of an overheard conversation leading to one big misunderstanding after another. Often involving sex.

In the second unaired pilot, written by Don Nicholl, Michael Ross and Bernie West, the plot took on more of the original British Man About the House, with David renamed Jack Tripp (the original series lead was Robin Tripp) and made a chef, Jenny becoming florist Janet Wood (played by Joyce DeWitt), and Samantha becoming Chrissy the secretary (then played by Susan Lanier). They’re on the beach, in Santa Monica. And Jack already has moved in before the opening theme has finished scatting doo-dee-doo-dee-doo-doooooo.

But the network wanted a new Chrissy, and having found Suzanne Somers for the part, they moved the show’s location to San Diego and the rest was TV history.