"Julianne is killing life right now," Derek, who's currently dating Dancing With the Stars troupe dancer Hayley Erbert, told ET's Leanne Aguilera. "She is just killing it! Her wedding was literally the best week of my life. It was the most fun, exciting and perfect, perfection, beautiful, magical thing I've ever experienced.
"I'm not going to lie, I was like, 'I'm eloping in Vegas, because there's no competing against this wedding,'" he continued. "There's not! Unless I have her plan it, so we'll see."
After Julianne and Brooks said "I do" in July, the two hit the road for their honeymoon. The lovebirds documented their romantic getaway via social media, and Derek admits even he was pretty envious of their trip.
"Yes, their honeymoon photos were pretty," he said. "It's actually kind of a joke. It was actually a joke, because we [all] spent so much time together [around the wedding]. I was joking, like, 'Oh, you're going to take me, right? For the honeymoon? I'm going to be there.'"
"[I was] joking around, like, how I'm going to pop up, you know? And there was a little bird that flew in on their breakfast every day, this little bird that would, like, eat their food," he added. "They called it, they named it Derek. 'Oh, it's Derek.'"
Meanwhile, Derek has been busy judging NBC's World of Dance with Jennifer Lopez and Ne-Yo, an experience he says has been "amazing" in its first season. He said when the cameras aren't rolling, Jennifer's usually "getting glammed up."
"Ne-Yo and I are usually around the audience, messing around, dancing and singing for them," he revealed. "She kinda misses out on the party sometimes because she's busy. She's Jennifer Lopez."
And by being a part of the show, Derek's watched another adorable couple fall in love right in front of his eyes -- Jennifer and her new beau, Alex Rodriguez. The former MLB pro isn't technically involved with WOD, but judging from the pics we've seen on J. Lo's Instagram, it appears he enjoys spending a lot of time with her on set.
"I get so nervous talking about other people's relationships," Derek said. "You know what? He's awesome. What a great guy."
"I'm super happy for them and the problem was… Jennifer, she was like, 'Derek, you've enlightened me. You've opened my world,'" he joked. "It kinda got uncomfortable, and then once A-Rod came I had to go, 'Dude, you gotta stop, Jennifer. Sorry, you got A-Rod now...' I'm just kidding!"
So what's A-Rod like as a dancer?
"I don't know," Derek replied, when asked if Jennifer's ever given Alex dance lessons. "Who knows! Here's the thing, once you've had a few tequilas, everyone's a dancer. You know what I mean?"