Around the World with Willy Fog (original Spanish title La vuelta al mundo de Willy Fog) is a cartoon version of Around the World in Eighty Days by Jules Verne.
After a recap of their Journey Around the World in 80 Days, Lord Guinness introduces Willy Fog to Professor Lidenbrock, who believes it is possible to travel to the Center of the Earth. Fog and Lidenbrock decode a note written by Icelander Arne Saknussemm detailing his own journey, and the pair decide to follow in his footsteps. The disbelieving Sullivan - now running a Betting Shop, having been sacked at the end of the previous series - refuses to believe it possible and bets another 20,000 pounds that Fog will fail. The villainous Transfer reappears and offers to help stop them. Again.
Fog, Lidenbrock and Rigodon set off for Iceland, but forget their train tickets; Romy and Tico arrive at the last minute with the tickets, and accompany them to Iceland intending to stay there and wait for Fog et al.'s return from the Center of the Earth.
Fog hires Hans to guide them on their journey, but Transfer takes his place intent on sabotaging the trip.
Hans and Rigodon continue to search for Romy and Tico. After a fruitless search, Hans accidentally finds an underground sea and interconnected series of tunnels/slides linking the underground cavern system. Reunited again, the group encounter a prehistoric monster, and Professor Lidenbrock blunders into some quicksand.