Gadzooks, called "Zookie" by family and friends, is David's special writing dragon, made by Elizabeth Pennykettle when he first moved in with Lucy and her. When Gadzooks is first shown to Lucy and David, the young girl asks the intelligent question "Why does he got a pencil and pad?" David remains adamant that he can neither draw nor write, but Liz says that Zookie "definitely wanted a pad to write or draw on".
Gadzooks writes things on his pad that come to him and sends this to David telepathically. He is David's main asset when it comes to writing Snigger and the Nutbeast, which originally started out as a birthday present for Lucy, and later David's second book, White Fire, which is about polar bears. Gadzooks helps David with plot ideas and comes up with (or discovers the real) names for many of his characters, including Snigger, Caractacus the crow, Ingavar, and Thoran.Gadzooks is seen as an intelligent dragon and a leader. He also apparently has psychic powers of some sort, able to see into the future and predict the death of Conker, and correctly guessing that Caractacus was responsible for attacking Conker and taking his eye. Gadzooks also told Zanna the name of G'lant , the invisible "Valentine" Dragon. Gadzooks is one of the most special, important and respected dragons of the Pennykettle household. In Darkfire as the evil Ix shadow takes control of his pad, possibly indicating he took control of his powers. But he wrote the word Sometimes... Sending out a beacon. In Fire World, Eliza creates him for the Librarium Gadzooks knows about the other world, much like Angel. In The Fire Ascending, like all the other dragons, he dissapeared, but Agawin/Alexa brings him back and allows him to re-create the arctic. At the very ending he appears on Liz's grave.