A Rigellian hypnoid in its natural form
The Rigellian hypnoid is a pink, six-legged reptile, native to the Rigel system.
Rigellian hypnoids have the ability to create illusions in the mind of bystanding observers. Harry Mudd used a Rigellian hypnoid to trick miners on the planet Motherlode into believing that his love potion crystals would make a woman fall in love with himself, causing the shapeshifting creature to assume the appearance of Lora. The swindle was exposed by the miners, however, and the Rigellian hypnoid was unmasked. (TAS: "Mudd's Passion")
The pink coloration and six-legged nature of the hypnoid was not scripted; in the final draft script of "Mudd's Passion", the hypnoid is described simply as "a small, reptilian creature".
The novelization of "Mudd's Passion" (published in Star Trek Log 3) describes the hypnoid's reptilian form as "about a meter high."