From the Super Mario Wiki
The Jellyfish Sisters, Gigi and Merri are the owners of a relaxation center of Gwarhar Lagoon in Mario & Luigi: Superstar Saga. When Mario and Luigi arrive at their relaxation center, the Jellyfish Sisters give them hand massages, and possess the powers of the Firebrand and Thunderhand. Gigi wears red while Merri wears green.
After Mario and Luigi learned their Firebrand and Thunderhand ability, the sisters teach them new moves to use with their techniques, such as being able to walk sideways or run quickly. The sisters then ask the Bros to find the twin Pearl Beans, situated in the cave they are in, as payment for the lesson, or pay a hefty price of 100000 Beanbean Coins.
The Jellyfish Sisters are also able to fly or at least glide, as they descend from the sky when they appear to the Mario Brothers.
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