Craig Bartlett created Cynthia off of Rugrats which first appeared in "Gram Canyon."
Arnolds "football" head and hair is Heradity. He got his hair from his dad, and head shape from his mom.
Helga seems to be to only one who calls Arnold Football head. Everyone else calls him Triangle face, or weird headed kid.
Helga calls Arnold Football head. But, Harold has a similar shaped head, but she calls him "pink boy" and/or "fat boy."
Craigs Wife, Lisa should get all the credit for the romance between Helga and Arnold. She suggested it to Craig one day and after that, history!!
Helga keeps that giant bow on her head because the first thing Arnold said to her was "I like your bow." Which was in preschool.
Craig Bartlett plays numerous animal voices in the show. Including Abner, Arnolds pet pig. He also plays Brainy, (Helgas annoying stalker.) and Nocturnal Ned. (The Radio DJ)
The city, that is nameless, is supposedly a mix of Seattle, LA, and Portland.
Frasier and Arnold have many similartys. Arnold supposedly lives in Seattle, while Frasier also lives there. And The thing between Niles* and Daffany, is between Helga* and Arnold.
Arnold first appeared in the Simpsons comics. Then in 3 claymation shorts which still air on Sesame Street.