"The character was fun to do because it was this blend of sexy and a church lady," she says.
"That's what sold me on doing the movie."
There are points, such as when the witch inhabits the woman's body, that Thompson plays the role with such unabashed fun she ends up skipping through the scene. She also had fun with the Southern accent, which to her is as much about attitude as it is about how you sound.
Those kinds of decisions are what Thompson likes to make when she agrees to do a role. Although the film is based on teen novels by Margaret Stohl and Kami Garcia, Thompson opted not to read the books before the filming started. She wanted to discover the character on her own.
One of the scenes in which she gets to have the most fun is a showdown between her character and the one played by Jeremy Irons. Although Irons and Thompson have worked a similar number of years, Beautiful Creatures is the first time they have worked together. The pair share a wicked scene in a church where their characters get to do a lot of posturing.
Thompson praised Irons for being the strong acting partner who helped her get the most out of the scene. Irons returned the compliment, saying that it's lovely to work with great actors.
"It makes acting fun."
There's a heavy fantasy element to Beautiful Creatures, which also stars New Zealand director Jane Campion's daughter Alice Englert, but director Richard LaGravenese was determined to use as little computer-generated imagery as possible. That put extra pressure on Thompson.
"When we got to the scene where I had to make this transformation, I did it all with just my face. I was able to do that because it's just like something that we would do in the theatre, where we don't have those special effects," Thompson says.
She started her career on stage, but she made the jump to films in 1989 with Richard Curtis' romantic comedy The Tall Guy. That film opened the door for Thompson to be in the Christmas classic, Love Actually, also written by Curtis.
Thompson's career is heavy on drama. But those who have worked with her agree she has a wonderful sense of humour.
Emmy Rossum, who plays another wicked witch in Beautiful Creatures, says: "You can't get a more fun human than Emma Thompson. She's intelligent, sensitive, smart, hysterically [wet]-your-pants funny."
Movie preview
Who: Actress Emma Thompson
What: Beautiful Creatures, opens in cinemas today.
- AAP