Common Side Effects Voice Cast & Character Guide

Common Side Effects' features some impressive starring performances from two actors who don't usually get to take the spotlight. The Adult Swim/Max animated series Common Side Effects is an off-beat but cutting satire of modern medicine and government, wrapped up in a morally-driven conspiracy caper. After discovering a potential cure-all that could save countless lives across the world, fungi expert and general oddball Marshall Cuso finds himself on the run from the company and government who want to keep his knowledge a secret.

Bolstered by strong animation, an impressive voice cast, and heady concepts that go beyond the typical limits of modern animated shows, Common Side Effects has been one of the best shows to debut so far in 2025. While the voice cast does include some legendary figures from animation, the central role of Marshall is played by someone more well known for their work behind the scenes than in front of the camera. Here is the cast of Common Side Effects, who they play, and where you've seen their work before.

Dave King As Marshall Cuso

Born June 6, 1978

Active Since: 2002

Actor: Marshall Cuso stars in Common Side Effects as Dave King, the central character of the animated series. Dave King has been working in television for years, but primarily behind the scenes as a writer and producer instead of an actor. Getting his start on Crank Yankers and Last Call With Carson Daly, King went on to write for shows like Workaholics, The Simpsons, Parks and Recreation, and English Teacher. He has appeared in many of those shows as a minor character. Common Side Effects is his first voice-over role, as well as his first starring role in a show.

Notable TV Shows Dave King Has Written For	Notable Episodes
Parks and Recreation	"Citizen Knope," "Two Parties"
The Good Place	"Help Is Other People"
English Teacher	"Field Trip," "Convention"

Character:Marshall Cuso is the lead character of Common Side Effects, a well-meaning expert on fungai who finds himself on the run. After discovering a mysterious new strain of mushroom known as the Blue Angel that can heal any and all illness or injury, Marshall risks his life to bring the potential cure-all to his former high school friend Frances. Marshall is Common Side Effects' main hero, even as the show shifts focus to other more morally compromised characters like Frances.

Emily Pendergast As Frances Applewhite

Born February 25, 1987

Active Since: 2013

Actor: Emily Pendergast stars in Common Side Effect as Frances Applewhite. Born in Youngstown, Ohio, Pendergast got her start in short films before making the move to television. Pendergast found her breakout role in season 7 of Veep, where she plays Beth, the wife (and half-sister) of United States President Jonah Ryan. She has since appeared in several films like Descendent, shows like We're Doing Good, and podcasts like Meet Cute.

Notable Emily Pendergast Films & TV Shows	Role
Veep	Beth
We're Doing Good	Nora
LaRoy, Texas	Kayla

Character: Frances Applewhite is the secondary protagonist of Common Side Effects. A former friend and classmate of Marshall, Frances went down a different path and finds herself working as an executive assistant for Reutical Pharmaceuticals, which seeks to stamp out any knowledge about the Blue Angel before it reaches the public. While Marshall is the driving force of Common Side Effects, Frances' attempts to wrestle with her own ambitions and sense of morality is the show's thematic core.

Mike Judge As Rick Kruger

Born October 17, 1962

Active Since: 1991

Actor:Mike Judge is one of the stars of Common Side Effects, as well as an executive producer on the show. Born in Guayaquil, Ecuador and raised in New Mexico, Judge's short film Frog Baseball introduced the characters of Beavis and Butt-head, who were spun-off into a show for MTV. The breakout success of Beavis and Butt-head led to the development of critically acclaimed shows like King of the Hill and films like Office Space. Judge voices characters in both Beavis and Butt-head and King of the Hill, and brings those talents to Common Side Effects as Rick Kruger.

Notable Mike Judge Films/TV Shows	Role
Beavis & Butthead	Creator, Beavis, Butt-Head, David Van Driessen, Tom Anderson, Additional Voices
King of the Hill	Creator, Hank Hill, Jeff Boomhauer, Stuart Dooley, additional voices
Idiocracy	Director, Writer, Producer, I.Q test machine

Character: Rick Kruger is a higher-up at Reutical Pharmaceuticals, as well as Frances' direct supervisor at the office. Initially presented as an aloof and careless executive at the company, the introduction of Blue Angel ends up causing a change in him. As the show progresses, Rick becomes a surprisingly reflective character after he learns the true potential of the mushroom — as well as the lengths Reutical will go to keep it hidden from the public.

Common Side Effects Supporting Cast & Characters

Common Side Effects Has A Supporting Cast Full Of Seasoned Character Actors

Common Side Effects has a fairly large supporting cast of characters who flesh out the setting and the personal lives of the characters with some impressive supporting players. Joseph Lee Anderson (Young Rock) and Martha Kelly (Baskets) play DEA Agents Copano and Harrington respectively, who find themselves investigating Marshall and becoming entangled in the conspiracy to keep Blue Angel secret. Frances' lazy boyfriend Nick is played by Ben Feldman (Superstore), while her dementia-afflicted mother Sonia is played by Lin Shaye (A Nightmare On Elm Street).

Marshall Kusso looking out at the screen and also staring at a turtle in Common Side Effects

Common Side Effects Creators On What Makes Adult Swim's New Conspiracy Thriller Unique [SCAD]

Common Side Effects is one of the most exciting shows coming out of Adult Swim in 2025, and the creators discuss the story with Screen Rant at SCAD.

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Danny Huston (Yellowstone) serves as the Common Side Effects' central overarching antagonist, Reutical board member Jonas Backstein, while Christine Ko (Dave) plays Kiki, a researcher at Reutical that provides favorable findings for the company. The most enigmatic character in the show is Hildy, Marshall's former mentor who wants the Blue Angel for her own ends. Hildy is voiced by animation legend Sue Rose (Pepper Ann). Common Side Effects has an impressive cast, serving as a great showcase for some talent that's rarely taken center-stage in shows.