"It's more fun to be mean than it is to try and make nice with everybody all the time," says the actress, who turns 51 next month.
The main motivation to sign up for the animation, however, was the star's young son, Louis Bardo Bullock.
The 5-year-old accompanied his mum on her recent trip to London, where Bullock attended the Minions world premiere.
But she decided against walking the red carpet with her son ("I would never take him to a premiere ... ") - in fact, Louis doesn't even know what his mother's day job is.
"I wanted to make something my son could see and watch and enjoy, even though he doesn't know what I do and he doesn't know it's me - I can sit in the theatre and watch him," she says with a smile.
"Nothing makes me happier than hearing that boy laugh. [There's] physical humour and animation, so hopefully I'll be able to do that."
Virginia-born Bullock, who came to prominence in the 1994 action movie Speed with Keanu Reeves, has eased her workload since adopting Louis in 2010.
Luckily, the filming schedule on Minions - which is set mainly in the 60s and boasts a star-studded cast including Jon Hamm, Michael Keaton, Steve Coogan, Jennifer Saunders and Geoffrey Rush - worked to her favour.
"I wanted to stay home and drive him to school, and the film-makers said, 'We'll come to where you are'. I was able to drop him to school, go to work and pick him up," she says.
Cinemagoers first met the yellow army of little loyal Minions in 2010, in the original Despicable Me film.
The banana-loving band of brothers enjoy causing chaos and are always on the lookout for villains to serve, so the ultra-glamorous Scarlet enlists them as her henchmen and tasks them with helping her snatch power from Queen Elizabeth (Saunders).
The film takes us from the US to Australia, China, India and eventually Britain, where much of the pandemonium unfolds - not least when the Minions try to steal the crown jewels from the Tower of London.
Former Mad Men star Hamm plays Herb, Scarlet's ever-supportive, mad- scientist husband who's usually found in his lab inventing gadgets.
Bullock was pleased by the pair's close bond in the movie.
"In an animated film, it's nice to see a good relationship between adults. Usually they are misfits, but what the film-makers created is a real partnership between Scarlet and Herb."
Next up for Bullock is the comedy drama Our Brand is Crisis, based on the 2005 documentary of the same name about the use of US political campaign strategies in the 2002 Bolivian election.
For now, however, she's looking forward to sitting down with Louis to watch her character cause a commotion in Minions.
"Now I understand how the people who play [Batman's] Joker feel. It's so good to be bad. It's nice. And I got paid for it!"
Who: Sandra Bullock
What: Minions, the spin-off from the Despicable Me films
When: Opens at cinemas tomorrow
- PA
