The proposal costumer recalls hilarious betty white in wedding

'The Proposal' costume designer Catherine Marie Thomas tells PEOPLE that Betty White was a highlight of working on the movie 15 years ago.

Some projects — and some people — stay with you long after you leave them behind. That was the case for costume designer Catherine Marie Thomas , who worked on The Proposal , which was released exactly 15 years ago on June 9, Starring Ryan Reynolds and Sandra Bullock , the film tells the story of an editor in chief, Margaret Bullock who needs a green card, so she enlists her assistant Andrew Reynolds to marry her.

The two lead characters have wildly different personalities, which Thomas balanced through their wardrobes, but she tells PEOPLE that one of her standout moments from filming came from the late Betty White. She's so funny, so sweet. But the wedding dress scene! It's hilarious. God bless her. In the scene, Margaret is gifted with Grandma Annie's White wedding dress, and she tries it on for Annie to tailor.

However, the dress doesn't fit her. At all. This is a comedy, after all. Thomas says White ad-libbed parts of that scene as they shot it over and over, making it funnier each time — and it was already funny to begin with. But at the core of the scene, Thomas still had a beautiful dress — that was actually two dresses. She loved the idea of having something really elegant but sort of covered.