“Rules of Engagement” (7 p.m., CBS) begins its sixth season tonight. That may come as a surprise to millions. The millions who have never watched or heard of it and the millions, or perhaps thousands (or dozens), who wonder why any series would kick off its new season on a Saturday night. The least watched night of the week.

Hardly the worst sitcom on television (or even CBS), “Rules” seems like a throwback. Its story about a long-married couple, a fresh young couple and a delusional “player” may remind some of “How I Met Your Mother,” but its jokes often seem more vintage. Characters often meet to swap stories at a local diner, not unlike some better-known comedies of the “Seinfeld” era. And the presence of Patrick Warburton (Puddy on “Seinfeld”) and “SNL” regular David Spade give it a decidedly ’90s feel.

Few shows have moved around as often as “Rules.” It began as a midseason replacement and returned as one in its second, third and fourth seasons. It had a full fifth season, but was moved from Monday to Thursday night midway. Now it airs as a Saturday night sitcom, the first new one to air regularly on this night in six years.

• It’s pariah night. Saturday offers two programs about some of the most scorned people on earth. “48 Hours Mystery” (9 p.m., CBS) returns to the Amanda Knox story. As was well reported this week, the young woman from Seattle was cleared by an Italian jury of the charges of murdering her British roommate. This occurred only after two trials and an orgy of headline attention in the British and Italian media, where tabloid sensation is the rule. The demonization of Knox, once dubbed “Luciferina” in the Italian press, continued right into the courtroom. Another “Mystery” (8 p.m.) also airs.

Closer to home, “Most Hated Family in America” (7 p.m., ID) looks at the family of Pastor Fred Phelps, whose Westboro Baptist Church has become notorious for picketing military funerals and other public ceremonies with provocative, hurtful signs and language decrying America’s doom and moral decay. The congregation consists mostly of Phelps and his family. Their radical approach to free speech has made it all the way to the high court. Directed by Louis Theroux, this film first appeared on the BBC in 2007.

Tonight’s other highlights

• On three episodes of “Harry’s Law” (NBC), Harry takes on an accused wife-murderer (Alfred Molina) (7 p.m.); Harry irks the D.A. (Jean Smart) (8 p.m.); a daughter’s testimony proves crucial (9 p.m.).

• The Texas Rangers and a team TBA meet in Game One of the American League Championship Series (7 p.m., Fox).

• Nebraska hosts Ohio State in college football action (7 p.m., ABC).

• Jed rushes to deal with some malingering tenants on “Bedlam” (8 p.m., BBC America).

• Ben Stiller hosts “Saturday Night Live” (10:30 p.m., NBC), featuring musical guest Foster the People.