"It's really annoying," she tells PEOPLE, chuckling. "I use 'whatever' all the time. Sometimes you just don't want to continue with a story and you just hope [people will] fill in the right blanks!"
Calling her experience working on the 1995 classic "the most fun I've had," Heckerling marvels even now at how hard star Alicia Silverstone – who stepped into the shoes of sweet and spoiled Cher – worked on set.
"We worked Alicia to death," says the director. "She was the one who had the least time for messing around. Every second she wasn't on camera, she was doing a fitting."
What did keep the star's spirits up even then was her beloved dogs. "[That's] one thing that kept her going," says Heckerling. "She had that big dog, Samson. She's a real, real animal person."
The goofballs on set were Breckin Meyer and Donald Faison, adds Heckerling. "[Working with] the boys was just like trying to get some puppies to sit still for a minute!"
Meanwhile, Stacey Dash "was more mature than the others," she says. "She had worked before in other movies, and so sometimes things would be kind of goofy or people weren't focused and she sort of was being patient. She was definitely the most professional."
All in all, the Clueless cast is still one Heckerling holds near and dear to her heart.