The first contestant on the dance floor was Robin Roberts, transformed as the “Frozen” character, Elsa, alongside Tony Dovolani and Elsa’s pal, Olaf, gamely played by ABC News' T.J. Holmes.
"We're going to ice the competition," said Roberts, as Elsa, who later in the show led a parade of mini-Elsas around Times Square.
"They love to make an entrance those two," said "GMA" correspondent Cameron Mathison, who hosted "GMA"'s Halloween "DWTS" Scare-tacular as the Frankenstein fill-in for “Dancing" co-host Tom Bergeron.
The next competitor on the dance floor was Amy Robach, dressed as a fierce and villainous Maleficent. Robach, who never cracked a smile, was paired with dance pro Keo Motsepe.
Proving she had her, "head in the clouds and no weight on her shoulders," Ginger Zee danced her way out dressed as pop star Ariana Grande, complete with her own glittered microphone. She gave the competition a scare when she immediately performed a dance routine with her pro partner, Sasha Farber.
"I think all the stars have one more problem," said Zee, as Grande. "I'm going to dance them under the table."
Making the most royal of entrances was the youngest competitor, Britain's Prince George, played by Lara Spencer. The 1-year-old royal heir was guided out on the dance floor in a gold-plated stroller by dance pro Karina Smirnoff, with assistance from two royal guards.
"I've only just learned to walk but I want to win the disco ball," said Spencer, speaking with a baby British accent. "I'm just a little baby."
The "stars" were chosen, it was revealed by Mathison's Frankenstein, after top-secret planning sessions involving the actual “Dancing” cast – including professional dancers Cheryl Burke, Karina Smirnoff and Derek Hough.
"GMA" viewers got a behind the scenes look at the "Dancing" pros viewing audition tapes for potential new cast members.
Robin Roberts auditioned as Beyoncé performing alongside Jay Z. Critiquing her performance, Hough said he would have “liked to have seen a little more bounce.”
“Hopefully this girl from [the film] ‘X-Men’ has what it takes,” Hough said, as Ginger Zee appeared as that film’s character, the mutant named Mystique.
Zee's audition was followed by one from Amy Robach who tried to dazzle the dancing pros with a Thriller-themed performance as a "Walking Dead" zombie.
"I think we should to move on from this one," Hough said.
Lara Spencer shimmied up next as the character, Groot, from the film “Guardians of the Galaxy."
"She only has one leg, which is a trunk," Smirnoff said. "Obviously there's not a lot of range of motion."
Once in Times Square, the "Dancing" stars became star struck themselves when the "GMA" weekend team arrived dressed as pop superstars One Direction. With Paula Faris leading the way dressed as Harry Styles, the whole gang - Sara Haines, Ron Claiborne, Gio Benitez and Dan Harris – lip-synched and danced to "Story of My Life."
"I love you so much," Wentworth as Amal Alamuddin screamed at Faris' Harry Styles character, giving her a huge hug and kiss to boot.
Other spooky segments on “GMA” included Michael Strahan’s scary elevator prank plus surprise visits from “Hot in Herre” singer, Nelly, who was disguised as the devil until his identity was revealed.
Football star and special "GMA" correspondent Tim Tebow also made a surprise visit, dressed as Maverick from the movie "Top Gun." Tebow gave the play-by-play as Spencer as Prince George and Zee as Ariana Grande tried to find their way out of a special corn maze set up in Times Square.
The final special guest was someone who knows a lot about Halloween, actor Miko Hughes, who played the Gage Creed, the child who died and was reanimated in the 1989 horror film, “Pet Sematary.”