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Memory Alpha

A Rigellian hypnoid in its natural form

The Rigellian hypnoid was a pink, six-legged reptile native to the Rigel system. They had the ability to create illusions in the mind of nearby 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 him, causing the shapeshifting creature to assume the appearance of Lora. The swindle was exposed by Spock, 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."