"I actually FaceTimed her 10 minutes after she gave birth," Johnson told ET after Monday's "Use Your Vote Night" on DWTS. "She had texted me as soon as I woke up at 6 a.m., and then I of course, being me, I was like, 'I gotta FaceTime her!' So that was me being really pushy."
"You know you're a best friend when you answer 10 minutes after [birth]!" Johnson added with a laugh.
Johnson called the newborn, "The most beautiful baby girl I've ever seen."
"I am just so proud of Lindsay, I'm so happy for her and Sam," Johnson told ET. "I cannot wait to get to Utah to snuggle that baby girl!"
Meanwhile, fellow DWTS pro Britt Stewart shared with ET that Arnold "texted me a picture of this beautiful baby girl" shortly after the delivery.
"I am just so, so happy for her! My heart is filled with joy," Stewart shared. "I texted her and I said, ‘Lindsay, that baby girl looks just like Sam, and that is good luck.'"
Pro dancer Artem Chigvintsev explained that he saw the post she shared to Instagram and commented, but wasn't able to speak with Arnold yet, because he and his celeb partner, Kaitlyn Bristowe, had to hit the dance floor for Monday's show.
"I just saw a picture, so I commented on Instagram. We had to go dance so I didn’t get a chance to talk to her but oh my gosh, that baby looks ridiculous! She looks so cute," Chigvintsev shared. "I’m so happy for her."
Judge Bruno Tonioli also expressed a message of love and support for Arnold while speaking with ET, sharing, "Congratulations, my darling. Well done! Another dancer. As I say, the more the merrier."
Back in May, Arnold revealed via Instagram that she was expecting her first baby. While speaking with ET just days after the announcement, the season 25 Mirrorball trophy champion confirmed that she would not be participating in this year's 29th season of DWTS due to her pregnancy.
"I will not be dancing this season, but I am hoping to be a part of the show in other ways," she said at the time. "I'll have our baby in November, which gives me about 10 months to have time with the little babe, and then get back into shape and get back into dancing to hopefully be back around for the next fall season."
"That's sort of the plan, and that's what I intend to do. I have every intention of coming back," she continued. "I mean, I love that show, I can't see me not wanting to be a part of it in some way for the rest of my life as long as they will have me."