Melissa McCarthy ad-libbed one of the most emotional scenes in 'Bridesmaids'

• McCarthy made up lines like having the clearance codes and fire crackers being thrown at her head.
• Director Paul Feig said originally, Annie talks out her issues with a collection-agency worker.
• "We were like, 'Why are we throwing this part away to a character we don't know?" Feig told Insider.

One of Melissa McCarthy's most memorable scenes in "Bridesmaids" was improvised, according to director Paul Feig.

In an interview celebrating the movie's 10th anniversary this month, Feig revealed to Insider the evolution of the feel-good scene where Annie (Kristen Wiig) gets an interesting pep talk from McCarthy's Megan.

As it turns out, Megan telling Annie about how her life has gone from having firecrackers thrown at her head in high school to now having the highest government security clearance was ad-libbed by McCarthy.

In fact, Megan wasn't even supposed to show up to Annie's house at all in the original script. Annie was set to get the pep talk from a woman at a collection agency who throughout the movie is trying to reach Annie about unpaid bills.

"Originally, there was a collection-agency character who would call Annie all the time because she was spending so much money," Feig told Insider. "That was going to be a running bit. This character, a woman in Mumbai at a call center, would always call, and Annie would always have some funny way to get out of talking to her."

The plan was to have the woman call Annie in that scene and read "her the riot act on her life," Feig said.

But that all changed once they cast McCarthy in the Megan role.

"We were like, 'Why are we throwing this part away to a character we don't know?" Feig said of how the scene was first conceived.

So the moment was rewritten to have Megan show up at the house and try to get maid of honor Annie back on track after Annie's big fight with her best friend, bride-to-be Lillian (Maya Rudolph).

Feig said there was a point while shooting where McCarthy began ad-libbing, and it resulted in the most memorable lines in the scene.

"She added in the stuff like how rich she is, having the clearance codes, firecrackers thrown at her head," Feig said. "That was all stuff she came up with when we shot on the day."

The scene is one of the few times in the movie where the leads have a genuine emotional moment between them, and for McCarthy, it proved she was in no way just a comedian - she could play up the drama, too.

It contributed to McCarthy getting a best supporting actress nomination for her work in "Bridesmaids."

"I'm just so glad we did that change," Feig said of the decision to spike the collection-agency character. "It really brought it all together and created this lovely friendship between the Megan and Annie characters. Because in movies like this, female friendship hadn't been explored this way before."