But less time spent on television and movie sets is fine with him. "I've stopped dialing the phone, though I'm still answering it," he says, seated in the University Art Gallery at San Diego State University, where his paintings were on view.Mull's droll wit has worked equally well in TV and movie roles. His list of credits is long and includes films like "Clue" (he was Col. Mustard), "Mrs. Doubtfire" and, recently, a repeat part as a quirky private investigator, Gene Parmesan, in the Fox series "Arrested Development."
"I have been so grateful for my opportunities. I found as an artist I had to have something in my career to supplement my income. My little niche of performing was it. In my case, this other alleged career has allowed me to pursue what I want to do with my art.
"If the audience (for the art) is there, I'm happy," he adds, "though I'm not necessarily paying my daughter's tuition with the sales of my paintings."
Before he had success in show business, Mull, now 63, trained to be an artist. He earned a Bachelor of Fine Arts (1965) and a Master of Fine Arts (1967) at the highly regarded Rhode Island School of Design. In recent years, he's devoted himself to his paintings, to a degree he hasn't since his student days.
"If I have found my voice, it has been in the last five years," Mull observes. "I knew I wanted to be an artist from 17 on. But I've been able to make more time in the last 15 years for my painting, painting every day I could, and something has happened."
The version of his exhibition "Adventures in a Temperate Climate" in San Diego concentrates on his paintings of the past six or so years. Co-organized by Tina Yapelli, the director of the University Art Gallery, and Libby Lumpkin, director of the Las Vegas Museum of Art, the now-closed San Diego show was pared down to 22 paintings; it was considerably larger in Vegas and will expand once again when it travels to the Figge Art Museum in Iowa.
"As you get older, you quit or get better," Mull says - though it's hard to imagine he ever thought quitting was an option. His relaxed demeanor cloaks an intense sense of determination.
"I've hit a point when the ideas for my paintings have mushroomed exponentially. I'm not sure why. Perhaps a sense of my mortality has something to do it."
He found his voice by time traveling to his suburban childhood in North Ridgeville, Ohio.
"I believe you should paint what you know and these were my formative years."
As Mull once quipped, "The town where I grew up has a ZIP code of E-I-E-I-O."
Well, perhaps E-I-E-I-O with a suburban overlay. And though Mull characterizes the American 1950s in which he was raised as bland, he has found a way to return to that era and make it vibrate with psychological tensions.
"Parents I" (2002) contains no adults; only a boy with shovel and an early version of Minnie with a cake in hand, towering above a Rockwellesque row of houses. ("Adults really were like overgrown children then," Mull says.)
"Grafton Revisited" (2003), whose title refers to his paternal grandmother's story about a brakeman killed by a train, pictures a steam engine, levitating above a track, a little off in the distance, and a girl, closer to the viewer, floating even higher.
The pictures themselves aren't personal; he's amassed an archive of mid-20th-century photographs from Life, Look and other sources. His wife Wendy and his daughter Maggie do all the legwork online to locate old magazines.
"Basically, I'm a troglodyte," he says. "I don't touch computers. I'd still use a rotary phone if I could."
There are very few family pictures to draw from, Mull explains. His parents didn't take many.
But the borrowed pictures take on personal dimensions in the process of using them, as with the prefab house in "Unseasonable Weather" (2005), which surely connotes his boyhood Ohio. The figure in the painting, wrongly dressed for the season, becomes a haunting emblem of a figure who feels alien to the surroundings.
"My work evokes photography without trying to imitate it," he explains. "It's about things that happen in photography. It's about working with photographs, not as a depiction of something, but as an object, like an apple in a still life. I approach these paintings, oddly enough, as a formalist, using the art school axioms of balance, space and structure."
You wouldn't expect Mull's gift for wit and parody in his acting life to be wholly absent from his art. His early photo-realist pictures done with airbrush toyed with the gap between appearance and reality. The dog bathing in "Dog in Tub" (1984) is no dog at all, but a ceramic tableau on a miniature rug. It's virtually impossible to determine scale.
"Fully Dressed Woman Descending a Staircase" (2004) is a slyly funny, handsome riff on Marcel Duchamp's iconic "Nude Descending a Staircase." In place of Duchamp's cubist/futurist abstract figure is a matronly woman in a staid domestic setting - the image framed by a floral border straight out of Eisenhower-era wallpaper.
Painted frames that are part of the painting itself are a frequent motif in Mull's paintings. Some display a single color, others have flowers or a little image in each corner and still others are floridly floral. About this device, he says, "The frame is one way of taking it out of present physical place, of taking it out of a present temporal space, too."
Another way he emphasizes the passage of time is to employ different shades of gray - grisaille, in art parlance - and to deliberately soften all or part of an image. In this, he's taken a cue from the major German painter Gerhard Richter, while giving the use of photographs a strong American accent.
No matter how serious Mull is - and has been - about his art, he seems resigned to the fact that he'll always have to deal with the notion of being the artist who is also a celebrity actor.
"People don't want really want you to be successful at more than one thing," he says, sounding matter-of-fact. "It's as if it causes resentment or confusion."
He sees the recent devotion to art simply as a continuation of the very thing he set out to do in his teens: make paintings. Over time, his love of painting has only deepened.
"My work has such a strong respect for the paintings that preceded it. I am not about to give up painting to make installations or anything else."
It's not hard to see why Mull has persevered as a painter. Nothing else has proved as fulfilling, though the work doesn't always progress easily.
"Painting is as pleasurable as going to see a good therapist would be. It's different than movies or shows, which are a group effort. This is something you do alone, with no interruptions. And ultimately, it's more rewarding."