Burton, 49, had already directed Depp in "Edward Scissorhands", "Ed Wood", "Sleepy Hollow", "Charlie and the Chocolate Factory" and animation movie "Corpse Bride".
"I've worked with him six times. I feel like I've worked with six different people," Burton said.
"There are a lot of people that really do a very good job maintaining their persona ... they are good at being themselves in a movie. I like character actors that like to become different people, that's what energizes me."
Depp stars alongside Burton's partner Helena Bonham Carter as Mrs. Lovett, who fills her popular meat pies with the remains of Todd's victims. The movie also features Alan Rickman as Judge Turpin and Sacha Baron Cohen in a cameo role.
Released in the United States on December 21, the film has earned $40 million, according to www.boxofficemojo.com. It premieres in London on Thursday and hits theatres around the world through January and February.
Burton's "Sweeney Todd" is gory and bloody, earning it an R rating that prevents under-17s from seeing it without an adult and adds to the challenge of marketing the movie.
Burton said he refused to water down his film to be "politically correct", and said the vivid color of the blood against a black and white background made it look obviously fake.
"It's bright red, and the last time I cut myself I didn't see that color."
