Three actors appeared in every episode: Katy Mixon (Katie), Diedrich Bader (Greg), and Daniel DiMaggio (Oliver). Meg Donnelly (Taylor) appeared in every episode after the pilot.
In addition to the above, the following actors appear in every season: Carly Hughes (Angela), Ali Wong (Doris), Carly Craig (Tara), Evan O'Toole (Franklin), Logan Pepper (Cooper), and Wendie Malick (Kathryn).
The show aired in a new timeslot with each season, and often multiple timeslots in a single season. It aired in three different Wednesday timeslots (8:30, 9:00, and 9:30) over its run, and the show aired on a Wednesday for at least part of every season except for its first.
Actor-Shared Background: Katie frequently mentions being a native Floridian. Katy Mixon was born in Pensacola, and does not do much to hide her regional accent.
Dawson Casting: Generally averted! The kids and teens are (for the most part) really played by kids and teens.
Taylor was born in 2001 and is played by an actress one year older. (Johnny Sequoyah, who had played Taylor in the pilot, was a year younger.) Her first boyfriend Eyo is played by Amarr M. Wooten, who actually was born in 2001. Her second boyfriend Trip, apparently one year older than hernote He's a senior in season 3, but has to repeat a grade (as he predicted he would) in season 4, putting him in the same year as Taylor; Anna-Kat also comments that she'll be 32 when he's 41 - as in, there's a nine-year age difference between them - whereas Anna-Kat and Taylor are only eight years apart, is a borderline case, as he is played by Peyton Meyer, born in 1998.
Oliver was born on January 17, 2004; Daniel DiMaggio, who plays him, is just six months older. His best friend Cooper (who is the same age as him) is played by Logan Pepper, just one year older. The effects of casting age-appropriate actors is evident with these two: in season one Cooper towers over the prepubescent Oliver but by season five both actors have grown considerably and Oliver is now slightly taller.
Even little Anna-Kat was initially played by an age appropriate actress, as she and Julia Butters were both born in 2009; however her replacement Giselle Eisenberg was born in 2007. Evan O'Toole, who plays Franklin, was also born in 2007, making his casting as Franklin (who is "nine-and-a-half" in 2019) a borderline example. Given the change in Anna-Kats and O'Toole hitting puberty hard between the fourth and fifth season, both Franklin and Anna-Kat were quietly aged up to be 12 years old at the end of 2020, making Eisenberg and O'Toole now just a year older than their characters, consistent with Donnelly and DiMaggio.
Fake Nationality: Doris is Korean-American ("Welcome to Koreatown", as she says in one episode), and is played by the Chinese-Vietnamese-American Ali Wong. This might be a recursive allusion to Fresh Off the Boat, a show she previously wrote for, where her friend Randall Park, a Korean-American, plays the Taiwanese-American Louis Huang.
Friday Night Death Slot: The show was moved here for the beginning of its fourth season, but when ratings held up better than expected it was moved back to Wednesday nights mid-season, where it would remain until it was cancelled at the end of its fifth season.
Hide Your Pregnancy: They hid both of Katy Mixon's pregnancies during the first two seasons. The only time either is addressed is in an episode that looks at how Katie's day would have gone based on what dress she orders online. Averted by Ali Wong, whose pregnancy was written into the show.
Hostility on the Set: Carly Hughes, who plays Angela, exited the show after season 4 because of, in her words, the "toxic environment" and "discrimination" that existed on the set. (Her appearance in the season 5 premiere had already been filmed before the COVID shutdown.) In the wake of her departure, a probe was launched which resulted in the show's creator Sarah Dunn stepping down from an active production role, the line producer being fired, and the showrunners having to undergo sensitivity training, a chain of events which couldve possibly led to the show being cancelled following the conclusion of the fifth season.
Real-Life Relative: In the episode "The Dance", Oliver visits a psychic. The psychic is played by Loretta Fox, who is Daniel DiMaggio's real-life mother.
Underage Casting/Writers Cannot Do Math: Katy Mixon, born in 1981, is technically old enough to be playing the mother of Meg Donnelly, born in 2000, although it would imply Katie had Taylor right out of high school, when the backstory makes clear Taylor was born to a Katie who was a college graduate (degree in marketing from Duke University) with a promising career - meaning she'd have to have been in her mid-20s at the youngest. This would work fine if Katie Otto was written as older, but all of the actors in the core family are playing characters roughly their own age, with Katie (like Mixon) not yet 40 as of 2019, when Taylor turns 18.
It's never been revealed why Johnny Sequoyah did not return to play Taylor after the pilot, but given how differently she played the character than Meg Donnelly, it's interesting to speculate on how she might have evolved. (Rumor has it that the two actresses were the finalists for the part, with Sequoyah ultimately cast for the pilot; when she didn't test well, producers decided to re-cast with the runner-up, Donnelly.)
Logan Pepper has said that he auditioned for a role before the producers brought him back to read for Cooper Bradford. Considering that Cooper is just about the only constant in Oliver's life outside of his own family since season 1, and even moves in with the Ottos in season 5, he's probably grateful he didn't book that other role.
Written-In Infirmity: After Timothy Omundson suffered a stroke, Stan was initially written out by divorcing Chloe for a woman half their age. A couple years later he wanted to get back into acting despite now walking with a cane and having a paralyzed left arm, so Stan suffers a stroke that causes his new wife to ditch him, so he comes crawling back to Chloe.