Fluffles are a species of underground animals in Kuu Kuu Harajuku.
According to Pink, the fluffles are a scientifically advanced species who fled underground as they didn't feel as though they belonged in co-existence with humans. They created an entire city underground Harajuku consisting of advanced architecture and winding tunnels. There is a prophecy that one day, a human with advanced scientific abilities will descend from the surface and rule the tribe as their queen.
In G, This Is Awfully Deep the girls meet the fluffles after a sinkhole opens up sending them underground. The fluffles are initially hostile to HJ5 (who they refer to as "serfies"). The only exception is Love, who they appreciate her extensive scientific knowledge. They believe she fulfills the prophecy and honor her as the queen, while shunning her friends by locking them in a cage over lava.
Even though Love feels like she belongs with the fluffles, she mentions that she loves being a member of HJ5 because they respect each others' differences.