AceShowbiz -

Vincent Kartheiser is a man with plans. Knowing that it would take much courage and confidence to ask Alexis Bledel for her hand in marriage, Kartheiser practiced his proposal first on "Mad Men" set with co-stars Jessica Pare and Elisabeth Moss.

"It was purely comedic but he was giving [Elisabeth] and I a facetious rendition of his planned proposal," Pare tells PEOPLE. "We were like, 'Great! Let's do this one without cursing and without yelling!' "

Moss, who plays Peggy Olson on the AMC series, feels happy for the spouse-to-be. "They are such a yin and yang! I love them both!" she says. Having known "Vinny" for 12 years, the "West Wing" actress clearly sees how he has changed since being engaged. "I've never seen Vincent like this. They are so happy. It's really cool!" For the bride-to-be, the 30-year-old star has something nice to say, "I'm kind of obsessed with her. She's the sweetest!"

Similarly, Kartheiser's on-screen wife Alison Brie cannot be happier to know that her on-screen husband is engaged to Bledel, who plays his mistress on the series. "My Twitter feed was abuzz today with [fans] going, 'Oh my God,' " Brie said. "I think everyone thought I was going to be very jealous but I'm excited for him for the record!"

Bledel's publicist Meghan Prophet confirmed on March 20 that Kartheiser proposed to Bledel after dating for one year. They made a public appearance in October 2012 when they attended The Macallan Masters of Photography collection opening at The Bowery Hotel, New York.