“Mad Men” creator Matthew Weiner is notoriously secretive about the twists and turns his series will take, but it appears the show’s fifth season will spend some time thinking about 1960s American Jews.

On Sunday night’s episode — the third of the new season — the series’ fictional advertising agency hired Michael Ginsberg, its first Jewish copywriter. (“Turns out everybody’s got one now,” remarks senior partner Roger Sterling.)

It’s unclear what sort of role the character will play — he’s already won over Don Draper, the show’s protagonist, and it’s possible things will take a romantic turn with Peggy Olson, the agency’s first female copywriter. But it looks like “Mad Men,” whose fifth season takes place in 1966, is also interested in Ginsberg’s home life, having already followed him to the apartment of his father — who speaks with a heavy European accent and blessed his son in Hebrew on Sunday’s episode. Presumably the senior Ginsberg’s background will come into play on a later installment, although at this point we can only guess how.

Played by Ben Feldman, Ginsberg may be the first major Jewish character to work at the ad agency, but he’s not the first on the series. During the show’s inaugural season, the serially adulterous Don Draper cheated on his wife with department store heiress Rachel Menken, whom he consulted about a campaign to promote tourism to the still fledgling state of Israel. (As part of his research, he also read Leon Uris’ “Exodus.”) But those Jewish subplots have largely faded in recent seasons, which have emphasized the gender and racial politics of the period.

That focus looks set to continue during the new season: In addition to Ginsberg, the ad agency has made another first-of-its-kind hire — a secretary so far known only as Dawn, the firm’s first black employee.

Now half a decade old, “Mad Men” is doing better than ever. Last month’s season premiere drew 3.5 million viewers, a 21 percent increase over the start of the previous season, and a series record in the ratings.

While those numbers are modest compared to network viewership — “Mad Men” runs on cable — the show enjoys significant cultural cachet, inspiring a number of other TV shows and winning the Emmy for best drama series in each of its first four seasons.