But imagine being director George Miller - also the man behind films such as Mad Max and Babe - and having the job of reining in motormouth Williams when he's off on one of his improvisational tangents. Although, says the affable Australian, who is double-teaming with Williams today at a Sydney hotel talking to media about penguins, elephant seals and the like, it's not a matter of controlling the actor.
"I think," says Miller, who has a touch of the mad scientist about him with his wild greying hair and round spectacles, "the best analogy is Robin's ... that it's like jazz."
And with that Williams, who also reprises his role of Barry White-style penguin Lovelace in the film, takes over: "You riff off each other, but you have to have that bassline, which is the script, that gives you the freedom to go off.
"It just gives you that moment when there is open field running and, 'he shoots, he scores'. And that's the idea with jazz: it's a solo, bang, and you've got people who are so good that you know you don't have to carry them and you can just back off and go, 'Yeah'. Oh, it's wonderful, and he [Miller] picks [the best] stuff and you know you are in the hands of a great conductor."
Though Happy Feet Two might not quite have the pulling power of the first film, it's still a rollicking, action-packed musical adventure. It had a tough time at the US box office in November because it opened on the same day as the latest Twilight film.
This time round, Mumble (Elijah Wood), the hot-footing star penguin of the first Happy Feet, is now a dad and struggling with the intricacies of bringing up his son Erik (voiced by young American actress Ava Acres). When Erik gets embarrassed because he can't dance, he and his mates take off from Emperor-land and meet up with Ramon who they follow back to Adelie-land - and so begins Erik's search for a role model and Mumble's to be a good dad.
Oh, and they also have to save the Emperor penguin colony from imminent destruction.
Along the way we meet other characters such as Ramon's crush Carmen ("He's like me in real life, I got lucky and found a tall one," says Williams of his third wife Susan Schneider who he married recently); the Mighty Sven, a flying "super penguin" voiced by Hank Azaria; and new characters Will and Bill, the bickering krill played by Brad Pitt and Matt Damon.
So how did Miller go about following up his Oscar-winning animated classic.
"In a weird way you don't have a choice," he says. "By the time we got into the last year of the first movie this story started to form in my head. And then at a certain point the first film does well enough where you have the option to do [a sequel] and because the technology was improving, and advancing so rapidly then we were able to do a lot of things that we weren't able to do in the first movie."
The addition of Will and Bill, and their giant "swarm" of microscopic mates, are ideal subjects for the 3D experience.
"To be stuck with the krill underwater is almost extraterrestrial - even though it's aquatic," says Williams. "as a diver it gave me the feeling of, 'Woah'."
Miller plays down the 3D aspect of the film saying it was very much about keeping it about the story.
"But what 3D does do is, it's like the audience in the cinema is travelling around in a kind of a capsule, like a spacecraft where you can move right down into the tiny microscopic world of the krill, or in the face of a big elephant seal, or fly above Antarctica and you can almost reach into the screen through a window."
You can tell Miller is proud of the Happy Feet legacy, especially the way it so accurately depicts Antarctica. "The characters, the ice, the snow, and everything all behave more or less as they do in nature."
And for him the films also have a more sentimental impact: "I often say that these stories are for the adult in the child and the child in the adult. I think one reason why Happy Feet resonated is that it had a kind of nourishment to it, with the ideas of being true to yourself, being brave, and trying to treat the world and yourself with respect."
LOWDOWN
Who: Actor Robin Williams and director George Miller
What: Happy Feet Two in cinemas Boxing Day.
