Hadid, 22, and Malik, 24, went as the Marvel characters Black Cat and Spider-Man, respectively. The model shared a photo on Instagram of Malik about to sweep her off her feet while in costume.
"Spidey's girl," she captioned the picture. "HAPPY HALLOWEEN from #FeliciaHardy, The Black Cat xx."
Irwin, 19, and Powell, 20, meanwhile, dressed as the DC Comics characters Lois Lane and Superman. The couple posted photos of their looks while celebrating in Irwin's home country of Australia.
"Clark Kent....? #Halloween," Irwin wrote.
"I have the most beautiful Lois Lane in the world!" Powell captioned the same picture on his own account. "Happy Halloween everyone."
Grande, 24, and Miller, 25, also rang in Halloween as Katinka (Milla Jovovich) and Mugatu (Will Ferrell) from the 2001 film Zoolander. The pair wore elaborate makeup and costumes, including a stuffed version of Mugatu's dog.
"relax Derek," Grande wrote alongside a photo on Instagram.
Elsewhere, Gellar and Prinze dressed up as Andie Walsh (Molly Ringwald) and Philip F. "Duckie" Dale (Jon Cryer) from the 1986 movie Pretty in Pink. The actress posted a picture of herself and Prinze posing at home.
"They didn't kill me - #prettyinpink #Andie #ducky @mollyringwald #joncryer @realfreddieprinze," she wrote.