For the first time ever, the city's young trick or treaters will be able to knock at Gracie Mansion's door and have some spooky fun with the mayor and his family.

Bill de Blasio and first lady Chirlane McCray announced Wednesday a Halloween Party at his house Tuesday for New Yorkers 12 and under that will include trick or treating and a tour of the 215-year-old house. Registration closed within an hour and the city set up a waiting list to try and meet the demand.

Experts said the party is a perfect way for de Blasio to improve his transparency and show a more casual side of his administration.

"He said he wanted the family and house to be expressible with more New Yorkers," said Christina Greer, an assistant professor of political science at Fordham University. "This goes along with the initial message that he put forward to New Yorkers.

Rebecca Katz, the mayor's spokeswoman, said said the "spooky walk" will give the hundreds of expected young visitors an interesting tour at the house and grounds, which will be transformed into a haunted mansion.

De Blasio and McCray promised that they will dress up but it wasn't clear if they will redo their pirate outfits from this year's Mermaid Parade.

"It is his favorite Halloween costume," Katz teased.

The spokeswoman wouldn't give further details about the party, especially the look of the house, but Seri Kertzner, who co-owns Little Miss Party Planners offered some suggestions.

Aside from black and orange balloons, Halloween themed plates and cups and, of course, plenty of snacks and candy, the party should include one-of-a-kind decorations that will set it apart from the other events going on in the city, according to Kertzner.

The party planner, who also blogs about family-themed parties, acknowledged that painting the walls to the renovated historical site would be tricky but there are other options like spelling "things out in marquee lights, to draw attention in the space, like spelling out boo."

Greer said tricking out Gracie Mansion isn't a silly idea by the administration and is more genuine with de Blasio who has always shown a fun side with his family. She added that although he probably won't use the party to promote his political agenda, he is still doing a big civic duty by educating kids about the Gracie Mansion's history.

"Opening up civic engagement for a bunch of kids will be influential for a lot of long lives," she said.