Scandal's Darby Stanchfield: Kerry Washington Approved My Olivia Pope Impersonation

Forget the president: As far as Scandal‘s concerned, fixer Olivia Pope is the most powerful person in Washington, D.C. – a challenging role that Kerry Washington pulls off every week.

Which explains why co-star Darby Stanchfield was nervous filming the episode that aired Thursday night, in which her character, Abby, stepped in as Olivia’s proxy to help handle the incessant drama swirling in the White House.

“It was pretty crazy,” Stanchfield, 42, tells PEOPLE of trying to channel the show’s star. She even slipped into Pope’s signature style.

“Wearing that white coat, you can’t eat anything, you can’t sit down – it’s just impossible,” says actress, laughing.

But the biggest difference was being on the White House set.

“Over at the Olivia Pope & Associates set, we’re like middle school children,” explains Stanchfield, “Every time there’s a cut in the action, we joke and dance around, there’s show tunes and fart noises.”

At the show’s White House, the cast is understandably more serious.

“It’s more like grad school there,” she says. “The actors are studying and murmuring their lines in their own corner. It’s more like a chess game over there, but still a blast to work in.”

So what did Washington think of her understudy? “She watched from behind the monitor and gave her nod of approval,” Stanchfield recalls. “And later on she came in and joked about me taking her place, saying, ‘I do not like this at all, I protest vehemently!’ ”

The cast wrapped filming this week, and the talk of this season has been how Washington, who’s pregnant with her first child and due any day now, hid her growing bump on the show.

Thursday night’s episode even featured a steamy love scene between Pope and Jack Ballard (Scott Foley).

“You saw it was only shot from the neck up,” says Stanchfield. “Camera tricks and body doubles, all of those were at play this season. Way to work with a pregnant woman!”

Scandal‘s season finale airs Thursday, April 17, at 10 p.m. on ABC.