Jason Butler Harner has joined the cast of Showtime's drama pilot Possible Side Effects, according to The Hollywood Reporter.

Meanwhile, two recurring players on It's Always Sunny in Philadelphia, David Hornsby and Artemis Pebdani, have been added to Fox's single-camera comedy pilot Boldly Going Nowhere, from the "It's Always Sunny" trio of Rob McElhenney, Charlie Day and Glenn Howerton.

RELATED: Ryan Reynolds Wants to Reboot Fantastic Four with It's Always Sunny in Philadelphia Cast

Tim Robbins' Possible Side Effects revolves around the Hunt family, which runs a pharmaceutical firm.

Harner will play the middle son, Silas, peacekeeper and perhaps the only sane member of the clan.

Boldly Going Nowhere from 20th TV, is about what happens day-to-day on an intergalactic spaceship directed by the rogue Capt. Ron Teague (Ben Koldyke).

Hornsby will play Lt. Lance Grigsby, the captain's devoted right-hand man, who supports his most misguided orders while dealing with a cheating wife and a thieving brother-in-law back home.

Pantheon-repped Pebdani plays Startemis, the female alien communications officer.