Frank Reynolds is the legal father of Dennis Reynolds and Dee Reynolds, and the ex-husband of Barbara Reynolds. Frank also lives with his alleged biological son (and ex-husband), Charlie Kelly.
He is a member of "The Gang" that owns and runs Paddy's Pub. He used to be prim and proper, but after he divorced Barbara, he let himself lose all convictions and live with no moral compass or decency.
Frank is portrayed by Danny DeVito.
- Frank is a successful businessman and has a long history of illegal operations and diabolical schemes.
- Frank styles himself a master manipulator and frequently takes the lead in the group's schemes.
- Frank has known many sordid characters throughout his life and around town, including a ring of Asian gamblers ("Charlie Goes America All Over Everybody's Ass") ("The Gang Gives Back") and various criminals and gangsters.
- He claims to have his children's best interests at heart but frequently exploits and insults them. He is especially cruel to Dee, constantly remarking negatively on her age and looks.
- Over the course of the show he has ceased to be a father figure to Dennis and Dee and is instead merely part of the gang.
- Frank wants to stay young. ("The Gang Reignites the Rivalry") He also may be the father of Charlie Kelly.
- Frank seems to take Mac under his wing, "mentoring" him on how to succeed in life via shady, unethical and sometimes illegal methods. It is observed that Mac looks up to Frank, more so than the rest of The Gang, though Charlie takes extreme measures to ensure that Frank remains his roommate.
- Frank has a tendency to trip on LSD, where he has manifested traumatizing experiences being trapped in the bathrooms of recreational vehicles. Like Mac, he drinks alcohol, but not to the excess that his young associates do, except in the episode "The Gang Gives Frank an Intervention."
- Though he clearly teaches life lessons and even offers valuable insights to The Gang, Frank's worldview is often very skewed. In the episode "Mac and Dennis: Manhunters", Dennis remarks that some of the stories Frank tells of his life come straight from John Rambo's life. In the episode "The Gang Gets Held Hostage", Frank emulates John McClane from the Die Hard film series. In the episode "Mac Is A Serial Killer", Dennis says Frank "makes less sense every day."
- Frank appears to be very wealthy. However, he prefers to live in squalor as Charlie's roommate in an apartment referred to by anyone who dares step into it as "a shit-hole," which originally stemmed from his desire to hide assets from his then-recently separated wife. Though Frank is egotistical, diabolical, and maniacal, he appears to have some good in him; he seems to care greatly for Charlie, possibly even more so than he does for Dennis and Dee. In "Mac and Charlie Die," he becomes grief-stricken when Charlie fakes his own death; he carries around a plastic likeness of Charlie through the streets while wailing and keening his love for him.
- Frank is a severe compulsive gambler, seen betting on everything from grade school basketball to Russian roulette, usually with his chain smoking, and high-stakes betting ring of Vietnamese friends. Sweet Dee once told Frank, "You can't just come in here and start running our lives like this, it's not fair!" to which Frank replied "Wanna bet?" Dee, confused, asks "Bet on what? Whether or not it's fair?" to which Frank replies "Yeah. Bet on whatever." This is a prime example of his boundless addiction to gambling, no matter how ridiculous the circumstances. "What's the action?" is Frank's signature line.
- Frank is known to frequently carry a revolver and wave it around at inopportune times.
- Frank has a brother named Gino who appears in Frank's Brother. Both were involved with the same woman.