Monday night’s episode of “Dancing With the Stars” was filled with spooky moments as the hit ABC series celebrated Halloween. But according to Season 21 pro Derek Hough, the scariest moment he faced throughout the chilling installment was when he had to turn his sweet partner Bindi Irwin into a sexy, blood-sucking vampire.

The two were tasked with taking on the Argentine Tango in Week 7, which they performed to Gerard McMann’s haunting tune “Cry Little Sister.” But to truly capture the essence of the fearsome routine, Bindi, the bubbly, animal-loving contestant, had to channel her inner demon.

“What I had to tell her this week, I was like, ‘All right, Bindi. You’ve done the fun performance, the smiles and all that, I need you to get fierce,” Hough told E! News, explaining he was about to tell Bindi to unleash her sexy side but “felt awkward.” “I immediately retracted that. I was like, ‘I can’t say that word in front of Bindi. That sounds weird to me.’ ”

So, instead, Hough told his 17-year-old ballroom partner she would have to show the judges just how seductive she could be during their Week 7 performance. And to do that, Bindi revealed to the fan favorite pro she would need help from some wild predators.

"She's like, 'I'm going to think of a tiger. I'm going to think of a shark.' She said a shark and I'm like, 'I don't understand,’ ” Hough said before acting like a sexy shark on the dance floor.

But it looks like the shark trick worked because once Hough turned on the music, Bindi got into her creepy character. “I’m like whoa, whoa. OK, young lady. You’re allowed to do that for a minute and a half and then when the song finishes you go back to being my little Bindi,” Hough told Entertainment Tonight after Monday night’s installment.

The twosome earned a perfect score for the routine and high praise from the judges, who were surprised to see Bindi pull off such a seductive dance.

“I never in a million years thought that Halloween night was the night you would shine your brightest,” judge Carrie Ann Inaba said, adding the routine was full of sex appeal. Julianne Hough “wholeheartedly” agreed with her co-judge, noting  the performance was “something so strong and deep rooted.”

“Dancing With the Stars airs Monday nights at 8 p.m. EST on ABC.