The character of Mona Osborn doesn't exist in the comics and was created exclusively for this animated series.
The costume party included people dressed as Medusa, Spider-Woman, Captain America, Black Widow, Hulk, Hellcat, Arkon, Storm, Sub-Mariner, Ms. Marvel, Power Man (Luke Cage), Wasp, Yellowjacket, Scarlet Witch, Vision, Thor, Phoenix, Dr. Strange, Black Panther, Valkyrie, Thing, Falcon, Red Sonja, and Daredevil, as well as several Spider-Men.
The original comic book version (Earth-616) of the Green Goblin wears a mask and a suit that includes scaled arms and leggings. This version, set in Earth-8107, actually transforms into a scaly green creature. Hence his plan to change everyone on Earth into similar Goblin like creatures.