In Episode 28: "Teddy and the Mudblups", Teddy, Grubby and Gimmick find themselves at the all-too-familliar Mudblup caves. They are re-captured and Teddy comes up with an idea to get them out. They cover themselves in mud to look like Mudblups and find their way to the entrance. When they come out in the open, it begins to rain. The mud washes off of them and the Mudblups realize they've been tricked. Teddy and Gimmick make it to the Airship safely, but Grubby is slow and doesn't realize the Mudblups are hot on his tail.
Gimmick pulls out a crystal and aims it at Grubby. Placing it on a tray and refracting the light off of the crstal and onto Grubby, the effects of the crystal are not what he planned as Grubby begins to slow down. Teddy suggests turning the crystal around and trying again. When Gimmick does this, the cyrstal speeds him up and he just escapes the clutches of the Mudblups as the sun peeks over the horizon.
This solves the mystery of the fifth crystal. It allows one to go slow or fast, depending upon which way it is facing when the light is refracted from it. This comes in handy many times throughout the series when the trio find themselves in situations such as these.
Character Profiles I Crystals I The Quiz I Inventions I Image Sources I Episode Guide