"I was just in the studio with her her boyfriend, well now fiance, Taylor. He didn't say a word! He seemed a little effervescent, but he's always pretty effervescent... I know him very well," Sullivan revealed. "He's quickly becoming one of my favorite people, and he and Mandy are an incredible couple."
According to the 37-year-old actor, Moore shared the happy news with her co-stars right away in their Pearson family group chat.
"I've seen the sparkler, but I have not heard the story yet because I have not seen her yet," he explained. "She just sent out an alert over our family text chain, so I can't wait to hear about it."
"She just sent a photo and just wanted us all to know that this just happened, and so then we went on a response spree for about a day and a half," he added. "I'm a huge fan of GIF'ing! I GIF the s**t out of that text chain, and I feel like it's appreciated!"