Godzilla (ゴジラ Gojira) is the most famous Japanese movie monster and the star of his own franchise. He is first mentioned in the Dr. Slump series in the 4th chapter, titled "Dr. Monster".
Godzilla is first mentioned in one of Akira Toriyama's manga in Wonder Island. Gyaosu, Gala and Pagos play war between Ultraman and Godzilla while waiting for the new inspector they summoned at their police office, with Pagos disguised as Godzilla.
Godzilla is loved a lot by Professor Monster and Arale. Arale gives Professor Monster a lizard and says it is a baby Godzilla, the same way he did to Arale with Gamera. According to the cover of the guide Dr. Monster wanted, it states that Godzilla had a lover at one point.
Godzilla later makes an appearance in the series in the chapter "Scoundrel in a Skirt!", somehow flying in the sky while firing his atomic breath. In "Penguin Village S.O.S.: Part 1", Gamera tells Godzilla and Nekotora-7 about Dodongadon's arrival in Penguin Village. In "The Great Arale-Eye Caper: Part 1", he appears in along with King Ghidorah and Gamera as they go to the Norimaki Residence to play with Gatchan. Godzilla is seen among Arale's classmates in "The Big-City Student. It makes other cameo in Penguin Gran Prix, Part 1 and Discover The Countryside.
The Adventures of Tongpoo
Godzilla briefly appears on TV in the second Dragon Ball episode, "The Emperor's Quest". Mai mentions Godzilla when Tambourine is killed by Goku and speculates that he (Godzilla) may be the one killing King Piccolo 's underlings (they had believed Goku dead at the time). Later in the series, when Porunga is summoned in West City, one of the police officers wonders if it is Godzilla.
Godzilla's power level is not explicitly stated, but due to the facts that Mai believes that Godzilla killed Tambourine and that Goku at the time he killed Tambourine possessed a power level of around 180, it's safe to assume that Godzilla's power is over 180.