THERE are some moments in life that can be categorised as surreal. Watching one of the world’s most famous men impersonate an insect is one.

“They’re like millipedes but they have things that sort of stick out of them that taunt you as they’re about to bite you with their ass,’’ shudders Johnny Depp, recalling coming face to face with creepy-crawlies while shooting Pirates Of The Caribbean: On Stranger Tides in Hawaii.

Who knew Depp, charismatic, enigmatic and giant of the big screen, had a fear of bugs? But then it’s easy to forget movie stars are human too - even ones of Depp’s stature.

It’s 21 years since he wowed critics as Edward Scissorhands in the first of numerous collaborations with director Tim Burton.

Up until that point he was best known as the pretty boy Officer Tom Hanson in TV show 21 Jump Street, but Burton’s film provided him with the yearned-for opportunity to prove his versatility.

In recent years he’s achieved huge commercial success, delighting audiences with weird and wonderful incarnations such as the murderous but musical Sweeney Todd and the demented Mad Hatter in Alice In Wonderland – but it wasn’t always so easy.

An actor who readily admits to ‘a fascination with the absurd’, he’s always earned critical acclaim for tackling testing roles. But that hasn’t always equated to box office success, as proven by films such as 1994’s Ed Wood and 1997’s What’s Eating Gilbert Grape.

He’s even on the record as saying that he didn’t think any of his movies would ever make money.

“The weird thing is I haven’t changed a thing. The process is still the process that it always was; you just grab bits and pieces and out comes this weird little character you’ve created. The fact people decided to go and see a movie I was in was shocking,’’ says Depp.

The movie he’s referring to is 2003’s Pirates Of The Caribbean: The Curse Of The Black Pearl in which he introduced the irreverent pirate Captain Jack Sparrow to the world.

Depp has unashamedly fallen in love with his creation over the course of three Pirates Of The Caribbean movies and he returns to him once again in the fourth instalment, On Stranger Tides.

“When you’re done playing Captain Jack, there’s a real decompression getting out of the skin, because I like being in that skin,’’ says Depp, who turns 48 next month, though he looks like a man in his early thirties.

It’s four years since the last Pirates film, At World’s End, but Depp says it wasn’t difficult to breathe life into Captain Jack once again.

“I suppose with all the characters I’ve played, they’re pretty close to the surface and relatively accessible and Captain Jack arrives pretty quickly.

“A little too quickly sometimes,’’ he jokes.

“Basically I can’t shake him, he won’t leave me alone.

“He still keeps showing up at odd times, like when you’re dropping your kids off at school.

“He’ll just show up and I have to shoo him away.’’ Speaking in low, measured tones, Depp has a thoughtful, gentle presence, but he doesn’t take himself too seriously.

It’s no secret Depp used his long-time friend, legendary Rolling Stones guitarist Keith Richards, as inspiration.

“I was a little worried about what Keith was going to think because for a good portion of the time I was spending with him I was sponging as much as I possibly could to use for the character,’’ he says.

“To do scenes with him was just amazing, one of those moments that you go: ‘I’m really lucky to be here in this moment and I’m really lucky that I’m aware that I’m lucky.’”

Listening to the actor, you can’t help but think he talks about Richards in the same awed manner in which millions talk about Depp.

Take away the persona and he’s just a man like any other, one who gets wobbly when meeting his idol.

Captain Jack’s latest adventure brings him face to face with feisty female pirate Angelica, played by Penelope Cruz, who Depp starred opposite 10 years ago in Blow.

“The weird thing is when we saw each other again it felt like we’d wrapped the film the week before,’’ says Depp.

He laughs when asked whether Cruz finally managed to teach him some Spanish.

“She taught me the raunchiest Spanish,’’ he says. “It’s so foul I couldn’t bring myself to repeat it here and now. I’ll carry it on my back for the rest of my days.’’