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This episode begins with Murky battling a case of insomnia. Lurky's snoring is so loud that Murky can't sleep. He yells through a pipe for Lurky to shut up, but when Lurky yells back he's knocked into a bookcase. Books come crashing down on his head, and the one that lands in front of his face turns out to be very interesting. It says that the best way to deceive someone, is with the person they trust the most. So Murky gets the bright idea of making a robotic Rainbow Brite to fool everyone with. He stays up all night working on her, then determines that he needs Star Sprinkles to finish her, so he and Lurky head to Rainbow Land to get some.
Meanwhile, in Rainbow Land, Rainbow Brite and the Color Kids are doing some spring cleaning.
Out of their sight, Murky and Lurky are spying on Rainbow Land after snatching a few Star Sprinkles. A stray rainbow almost gets them, but Murky and Lurky duck just in time. Having what they came for, they head back to The Pits to put their plan into action.
Back in the lab, Murky and Lurky create a concoction using the Star Sprinkles, to make a replica of Rainbow's Color Belt. Murky reveals the finished product to Lurky and Lurky can't even tell the difference between the real Rainbow Brite and this imposter.
The real Rainbow Brite was busy at the Color Caves. Spring Cleaning had exhausted their supply of Color Crystals, so Rainbow, Twink and the Color Kids went to get more. They carried as many Crystals as they could, and asked Twink to bring more to the Color Castle as soon as he could.
Murky and Lurky heard what was going on and took this opportunity to deploy the robot. Lurky wound up the key sticking out the back of her head and Murky sent her into the Color Cave. Robot Brite told Twink to bring all of the Color Crystals to The Pits instead of the Color Castle. Twink was confused, but agreed. He noticed when "Rainbow" left, that the Color Crystals she stepped on broke to pieces. He figured either the Crystals weren't as strong as they used to be or that Rainbow had gained a lot of weight.
Moonglow and Nite Sprite were also on their way to the Color Caves to get more Color Crystals when they ran into Robot Brite. She told them the same thing - to bring all the Color Crystals they could carry to The Pits and not worry about making the nights beautiful. Her power ran down while speaking to them, but Murky was able to use a walkie talkie to impersonate Rainbow's voice. Moonglow found it very odd that "Rainbow" did not understand Nite Sprite's language, whereas she'd always understood it before.
Moonglow, Nite Sprite, Twink and the other Sprites followed Robot Brite's orders and took the Color Crystals to The Pits. Moonglow knows Rainbow hasn't been wrong before, so she must have a good reason for this now. Back in the Color Castle, the real Rainbow and the Color Kids are still busy cleaning, but are out of Star Sprinkles. They start wondering where Twink is when Moonglow and Nite Sprite show up. Moonglow explains that Rainbow told her to take the Color Crystals to The Pits, but the real Rainbow knows she never said that. Twink then appears and shares the same story as Moonglow. Rainbow knows Murky must be up to something.
Rainbow instructs Twink to go back to the Color Cave and get more Color Crystals, but to bring them to the Color Castle this time. He runs as fast as he can to the Color Caves, but Murky and Lurky see what's happening and beat him there. They deploy Robot Brite once again, who tells Twink to once again bring the Crystals to The Pits. Twink enters the cave, as the real Rainbow and Starlite watch from behind a rock. Starlite decides to play along and take the imposter into the cave as well to find out who she really is - while the real Rainbow also goes into the cave. The robot gets stuck as soon as they get in the cave, confirming Starlite's suspicion that she isn't real.
The Sprites are all upset, being given such mixed messages about the Color Crystals, so Rainbow tries to calm them down. But as soon as they see the fake Rainbow, they get upset again. They get Robot Brite down and explain to the Sprites what Murky has been up to. Rainbow tells the Sprites to use the other exit to leave the Cave, get the Color Kids and bring the Color Crystals back from The Pits. In the meantime, she has a plan to get rid of Murky using the few remaining Star Sprinkles.
The real Rainbow walks out of the Color Caves, but Murky thinks it's still the robot. He walks out to wind her up again, but can't find the key! Rainbow reveals herself as the true Rainbow Brite and uses the Star Sprinkles to chase Murky and Lurky away with a rainbow.
Finally, things are back to normal in Rainbow Land and Rainbow proves her identity by doing something no robot could ever do.