What sequel series continued the Ricardo and Mertz characters after I Love Lucy ended?

The sequel series that continued the Ricardo and Mertz characters after I Love Lucy ended was The Lucy–Desi Comedy Hour.

Rather than continuing the original weekly, half-hour sitcom, Desilu Productions created a collection of thirteen hour-long specials. They aired on CBS from 1957 to 1960 and retained Lucille Ball as Lucy Ricardo, Desi Arnaz as Ricky Ricardo, Vivian Vance as Ethel Mertz, William Frawley as Fred Mertz, and Keith Thibodeaux as Little Ricky.

The new format reduced the production schedule and brought in prominent guest stars, including Hedda Hopper, Danny Thomas, Red Skelton, Tallulah Bankhead, and Ernie Kovacs. The Ricardos had moved to Westport, Connecticut near the end of I Love Lucy, and the specials continued their family and social adventures there.

The title can cause confusion because the program originally aired under sponsor-related names, including The Ford Lucille Ball–Desi Arnaz Show. The Lucy–Desi Comedy Hour became the familiar title through later CBS reruns and syndication. It is the direct continuation—not Here's Lucy, The Lucy Show, or Life with Lucy, which were later Lucille Ball projects with different premises and characters.