But I'm no Biblical scholar. All I really knew about the story of Jonah was that he was some guy in the bible who (like Gepetto) was swallowed by a whale, survived for a time inside, and eventually escaped.
So I sought out the story. Here's the micro/Cliff's notes version: Jonah was a Jewish prophet whom God asked to go to the city of Nineveh and tell the people there to straighten up their act. Fearing the reaction of his people if he did, and fearing the retribution of God if he didn't, Jonah chose to run away, leaving Israel by ship. Soon, a huge tempest came, threatening to kill everyone on board. Jonah explains this is happening because of him and urges the crew to throw him overboard to save themselves, which they eventually do.
Unfortunately, once he was tossed into the sea, Jonah is swallowed by a giant fish. Fortunately, that fish is not big on chewing. Jonah finally repents for his sins and for shirking his duties and is forgiven by God who forces the fish to barf him back out onto land. Jonah then fulfills his duty and things end up great.
But what does this have to do with Pinocchio? Why did poor Gepetto get swallowed by the whale? I couldn't think of any sins Gepetto needed to repent or duties that he had shirked. Aside from whale-swallowing incidents, the pair seemed to have nothing in common.
Then it hit me: Gepetto isn't analogous to Jonah - Pinocchio is! Like Jonah, Pinocchio shirks his responsibilities. Instructed to go to school and learn to be intelligent, honest, and good, he instead runs away - first to join Stromboli's puppet show, and then again to Pleasure Island. After his hardships, Pinocchio learns Gepetto has been looking for him and has been swallowed by Monstro. Like Jonah, he sees that his selfish choices are causing danger and hardship for others, and like Jonah he chooses to be tossed into the sea.
Once there, he too is swallowed by a massive fish, and what does he do once he's inside? Like Jonah, he faces his creator (in this case, Gepetto), admits his sins, and asks for (and is granted) forgiveness.
The only thing that would make the whole thing neater was if Jonah had a talking cricket along for company.