Alice Cable: Her last name is shared by Swamp Thing cast members Matthew Cable and Abby Cable (born Arcane and after marrying Swamp Thing years later, Holland), neither of which appear in the story. Otherwise she's an original character and serves as Alec's love interest.
Anton Arcane: Unlike the original comic origin of Swamp Thing, in this issue it is Anton who causes the birth of the Swamp Thing, being the greedy businessman who's henchmen ambush Holland's lab and cause his death and rebirth as the Swamp Thing. Also, Anton later takes the formula himself to become Holland's nemesis. Apart from being Swamp Thing's enemy, bears little resemblance to his comic counterpart and would be more akin to General Sunderland.
Linda Holland: Alec's sister rather then his wife, thus allowing the Alice/Alec romance to begin before his transformation into Swamp Thing.
Swamp Thing: The least changed of the cast, Swamp Thing was quite similar to his comic character and apart from his supporting cast was essentially the same character as that in the comics of the time.