Holy moly, it's Danny DeVito! One of the most ubiquitous actors of the 1980s and 90s, and certainly the most physically distinctive, is standing in a blandly corporate hotel room in Whitehall, of all random places a stone's throw away from No 10 Downing Street.

"Hey, I'm Danny, nice to meetcha, thanks for coming," he says in a New Jersey accent that makes him sound a little like a comedy sidekick from The Sopranos.

Few actors have ever looked like they're having as much fun as DeVito. From playing Michael Douglas and Kathleen Turner's whirling dervish of an evil nemesis in Romancing the Stone, to sniping at Arnold Schwarzenegger in Twins, to waddling through his lair as the demonic Penguin in Batman Returns, DeVito has been chewing up the screen for as long as I can remember, hamming it up with the delight of a man who somehow lucked into his dream job. But even if you are not a fan of any of those films (in which case you are clearly mad), DeVito almost certainly formed the bedrock of your film-going life in the late 20th century. It was DeVito's production company, Jersey Films, that made such classic 90s movies as Get Shorty, Erin Brockovich, Reality Bites and Pulp Fiction.

"We put Miramax on the map!" he says with a Mutley-esque wheeze of a satisfied laugh.

In person, he is pretty much as he seems on screen: fast-talking, endearing, and, to put it bluntly, as tall as he is spherical. He describes himself as "five foot nothing" but, from my lofty vantage point of 5ft 4in, that seems a little generous. He barely comes up to my chest and when he later gives me a hug goodbye I have to bend at my hips to reach his embrace. As he himself has said repeatedly over the years, his height has undoubtedly helped his career – "No casting director is gonna forget the 5ft guy!" – and, in any event, the man can certainly fill the room. Despite suffering from travel fatigue and what sounds like the beginnings of a cold he is as full of beans in person as he has always been on screen. A single question often results in an energetic 20-minute answer, one that takes in everything from politics ("I'm so glad Bush isn't around anymore, that poor bastard") to imitations of Schwarzenegger ("'Cah-li-for-nya's gawt all dese pro-blawms' – ha!") to his brief early career as a hairdresser ("There were all these girls around – that was a good summer, hahaha!")

Danny DeVito in One Flew Over the Cuckoo's Nest (1975). Photograph: Moviestore Collection/Rex Features

"I'm 68 but I feel like I could do tons more things," he says, rubbing a palm over his bald pate, and it's a gesture he repeats tic-like throughout the afternoon. The hair that fringes his head has become a little greyer and tuftier over the years but, in the main, he looks, acts and sounds the same as he did in his breakout role over 30 years ago in the US TV show Taxi, which is about to be rescreened on CBS Drama.

Taxi, which ran from 1979-83, is one of the great American sitcoms, with the same kind of high quality and smart sensibility as MASH and Cheers. DeVito was utterly unknown when he was cast and, even though the show was essentially a vehicle (pun only slightly intended) for its star, Judd Hirsch, it was DeVito who stole it, although, he is quick to add, "that was all down to the writing". DeVito is a sweet mix of modesty about his personal achievements and bullish pride in the collective results, and there are few projects that give DeVito more retrospective pride than Taxi.

DeVito likes to develop a familial relationship with his cast and crew and he was with the Taxi family for five exciting years. As well as pretty much saving the show when it was threatened with cancellation in 1982 (he made a high-profile appeal on Saturday Night Live for it to be reprieved; another network picked it up), he produced and co-starred in the 1999 Jim Carrey film Man on the Moon, which was a biopic about one of his Taxi co-stars Andy Kaufman, who died in 1984, aged 35. Kaufman's style of humour – surreal, dislocative, joke‑averse – would seem completely at odds with DeVito's broader approach. But DeVito adored him and just the mention of his name prompts another 10-minute anecdote that sparks belly laughs and what sounds like a lump in the throat.

Another reason DeVito has such affection for Taxi is that his character, Louis de Palma, the despotic taxi dispatcher, pretty much established the template for his career: he has played variations on the role repeatedly, including in his current US TV show, It's Always Sunny in Philadelphia.

"Oh yeah! I always play to my strengths," he grins, happily grabbing the self-deprecation for the sake of a punchline.

Danny DeVito with Arnold Schwarzenegger in Twins (1988). Photograph: Allstar/Cinetext/Universal

But this suggestion that DeVito has been happy to coast creatively is clearly untrue. Aside from the sheer variety of his production work he has directed films as varied as Throw Momma From the Train (an 80s comedy riff on Strangers on a Train, co-starring Billy Crystal), Hoffa and one of the best literary adaptations of all time, Matilda.

"When I'm directing or producing, I like to do different kinds of stories. But you have to know what you really like and when you do, you have to front your position," he says.

DeVito loves telling tales about when he fronted his position. One of his favourites involves his struggle to get Pulp Fiction made. DeVito had loved the script for Reservoir Dogs so he told Quentin Tarantino to come to him with his next one. Tarantino duly obliged and sent him Pulp Fiction. DeVito, with characteristic enthusiasm, "was crazy for it" and bought it. However, TriStar, the studio with whom DeVito had a relationship, nixed it, deeming the film too violent.

"I was just incensed!" DeVito recalls. "I was like, you guys have made Cliffhanger with Stallone blowing things up – that's pretty violent! So I jumped up on the guy's desk and was screaming: 'You gotta make this movie! You gotta!'" A very unfair image of a hysterical Mini-Me leaping around an office pops into my head. "The guy was like: 'Get him outta here!' So then I called Harvey [Weinstein] and he saved my ass, and we helped establish Miramax."

DeVito is a dedicated and (unsurprisingly) vocal Democrat. His political persuasion, I suggest, must make for some awkward moments with his old friend Schwarzenegger.

"Oh yeah. If I read in the paper about him doing something as governor that I didn't like I'd just call him up and be like, 'Man, what the ffffff ... ?!'" hes says, letting the expletive trail away. In fact, DeVito had tried to talk Schwarzenegger out of running at all by pointing out that they would have to postpone making Twins 2, this time with Eddie Murphy as the third unlikely sibling: "I was like, 'Governor of California, here,'" he hovers his left hand just above the floor. "'Twins 2, here!'" And he raises his right hand sky high. Happily for cineastes everywhere, Twins 2 is now back on the cards and such battles haven't come in the way of their friendship:

"You know, deep deep down, I always felt that Arnold was a good guy ..." his voice drops a little uncertainly.

DeVito is a fiercely loyal friend and also among his closest chums are Michael Douglas (who he has palled around with for half a century) and Jack Nicholson (who grew up near him in New Jersey). "People come into your lives who you have a good time with, and time goes by and you still have a good time with them and you do stupid stuff with them. To me, that's life," he says.

Danny DeVito makes his West End debut in The Sunshine Boys last year. Photograph: Tristram Kenton

This combative and deeply loyal nature comes, he reckons, from growing up in an Italian family. "We were always getting into arguments about something, although it was mainly about music and girls and getting caught with cooking herbs," he grins. DeVito was the only son and had two much older sisters "who looked after Danny boy", one of whom offered him a job at her beauty salon when he finished high school. He did that for a while ("mainly shampoos, sometimes some colouring, I love being around women"). His sister then decided to send him to learn about makeup to broaden the business. So he obediently headed off to the American Academy of Dramatic Arts where he discovered that, actually, he preferred the acting classes to the makeup ones. "I had to tell my family," he says grimly, making it sound like he came out to them.

The importance DeVito clearly places on family ties and long-term relationships makes last year's news that he and his wife of 40 years, Rhea Perlman, have separated even sadder. Few couples have ever looked as temperamentally and physically suited as DeVito and Perlman, and their marriage was generally seen as a rare stable and happy one in Hollywood.

"Ah, Rhea and me? We're doing OK, we're still good buddies. We talk all the time, we're OK," he says, and for the first time in the afternoon he loses a little of his pluck and sounds somewhat deflated. Then, maybe because I look so stricken for him or maybe because he just needs it, he reaches up and gives me a big, long hug.

But DeVito hasn't been in this business for 40 years for nothing and he quickly recovers and tells happy stories about what a protective father he was to his and Perleman's three, now grownup children.

"Ah, I love 'em dearly. But the thing about kids is, if you raise 'em right, they leave you," he says. The words are sad, but DeVito grins.

• Taxi is on weekdays at 6.30pm from 7 March on CBS Drama on Virgin 197 / Sky 149 / Freesat 134