In the 23rd century, an enterprising trader named Cyrano Jones procured an interesting and adorable little creature. These tiny furry beasties had a calming effect on the nervous systems of humanoids – well most humanoids, anyway. They were called tribbles.

Cute furry robotic creatures that shake and quail when disturbed.
Two sizes, large (12″ in diameter and your choice of color) and small (6″ in diameter and come in random shades of black, brown and grey).
Is partial to quadrotriticale, but really likes AA and AAA batteries, conveniently included in its velcro-edged stomach.
On-off switch conveniently hidden inside the tribble!
Guaranteed to have a calming effect on most humanoids*