First season

Larry Alder (McLean Stevenson) is a radio talk show host who left Los Angeles after being divorced, and moved to Portland, Oregon, with his two teenage daughters, Diane (played in the first season by Donna Wilkes and in the second season by Krista Errickson) and Ruthie (played by Kim Richards). The supporting cast consisted of producer Morgan (Joanna Gleason) and engineer Earl (George Memmoli).^[1]

The first five episodes, shown at a later primetime slot, centered on Larry at the radio station and his smart-aleck remarks to callers. In these early episodes, Larry is described by Fred Silverman as "a buffoon, the cliché TV father".^[2] After that point, a "complete turnaround in the direction of the series" was made, concurrent with a move to an earlier time slot, to put the emphasis on the relationship between Larry and his daughters.^[2]

In its new earlier timeslot, Hello, Larry aired immediately after NBC's hit Diff'rent Strokes. In the hope of raising the popularity of Hello, Larry, crossovers were created between the two series. By episode 10, "The Trip: Part 2", Larry Alder and Phillip Drummond were revealed to be old Army buddies (with Drummond's company becoming the new owners of Larry's radio station).^[3] Some contemporary articles have incorrectly stated that Hello, Larry was a spin-off of Diff'rent Strokes, with the crossover episodes constituting a backdoor pilot;^[4] in fact, the Diff'rent Strokes episodes were broadcast while Hello, Larry was already on the air, and the relationship between Larry and Drummond was the result of retconning in both series.

Second season

The trend to focus on Larry and his daughters continued into the second season, with Morgan and Earl being seen less frequently. The show's opening theme lyrics in the second season were changed; the line “the calls are comin' in, you'd better start to grin” in reference to Larry's radio career gave way to “you're raising them just fine, but keep an open mind” when the stories became more focused on the Alder household.^[5]

In addition, various supporting characters were added in the apartment building where Larry and the girls lived; these included a neighbor, Leona (Ruth Brown), who usually did not approve of Larry's parenting; Tommy (John Femia), a purportedly worldly wise teenage boy who became a love interest for Ruthie; Larry's widowed father (Fred Stuthman), who moved in with the younger Alders; and former Harlem Globetrotters player Meadowlark Lemon as himself, running a local sporting-goods store in the series (believed to be an attempt to boost ratings with African-American audiences who had tuned in for Diff'rent Strokes).^[6] None of these changes, nor a two-part episode in which Larry's ex-wife Marian (Shelley Fabares) tried to reconcile with him, were enough to save the show.