AceShowbiz - Johnny Depp was left feeling lonely on the set of fantasy film "Alice in Wonderland" - because director Tim Burton forced him to act without his co-stars to gain the full impact of special effects technology. The Hollywood hunk is part of an all-star cast, including Anne Hathaway, Michael Sheen and Helena Bonham Carter, in the upcoming Disney production.

But because Burton required special effects to be added in post-production, Depp found himself acting alone in front of a green screen for many scenes. The star admits he found the process exhausting and left him utterly confused.

He says, "The novelty of the green wears off very quickly. It's exhausting, actually. I mean, I like an obstacle - don't mind having to spew dialog while having to step over dolly track while some guy is holding a card and I'm talking to a piece of tape. But the green beats you up. You're kind of befuddled at the end of the day."

But Depp is full of praise for his longterm friend Burton, "To choose to grab 'Alice in Wonderland', that in itself is one thing, and then to do it to the Tim Burton level is madness. It's so huge because, whether it's the CGI or the green screen or the 3-D or the live action, he's done it all here. It's the greatest undertaking I've heard of."