Ducktales - Earthquack (DVD)

Gyro Gearloose does a survey of Scrooge's property, and finds that the Futterman's Fault runs right under the money bin. To stave off underground damage, Gyro is given permission to install a giant shock absorber at the center of the fault. However, the work crew assigned to the installation refuses, when they say they can hear voices.

Scrooge then gets in a mine cart, and goes down into the Earth to find these voices, with his nephews close behind. What they find are a race of creatures called the Firmians, who can rolls themselves into balls, and bounce against walls. The large amounts of activity by the Firmians is what has been causing the earthquakes recently. However, it turns out these were nothing, as the Firmians are planning their 'Great Games,' where all manner of Firmians compete for a trophy dubbed the 'Crack Pot.'

Scrooge then steals the trophy, in hopes this will stave off further rolling. However, on his way back to the surface, Scrooge drops his hat, and the leader of the Firmians claims this as their new trophy, causing the games to continue. This causes a fissure to open, and eventually causes the Money bin to crack, and Scrooge's fortune to tumble down into the Firmian's caverns.

However, just when Scrooge thinks all is lost, the Firmians return his fortune to the surface, and leave through their underground tunnels, off to their next great games...in a place to the west called California.