Sparkle Day is the final episode of Season 4.
It's Sparkle Day - a special event - and Tiny leaves the daylight on for extra time for the celebrations. The Little Robots choose who gets to wear the Sparkly Crown and be made a fuss of. Everyone loves Sparkle Day except Rusty, who is too shy to sparkle. Tiny finds a way to turn her into the sparkliest Little Robot of all.
Tiny told Stretchy Rusty was too shy to join in.