Sparkle (also known as Ricky) is a baby who appeared in "BMO Lost." BMO found him in the forest and at first thought he was a carnivore. Upon discovering that it was a baby instead, it thought Sparkle was lost. So it tried to take him home with it until his mother came along and took him instead.
Sparkle briefly reappears in "Reboot," having apparently grown up to become a rugged horse whisperer (one of two careers Air predicted for him, the other being "sexy hitman"). He whispers some affirmations to a horse before sending it off, then is briefly startled by the mutated Susan Strong jumping by him, which causes him to exclaim, "Sparkle says 'What?!'".
He is a large baby wearing a white diaper and nothing else. His eyes are large and black, and he has no hair. Like his mother, his skin is salmon and the left hand is a flipper-like appendage. This flipper is used to create a distinctive call when pressed against the lips.
The pudginess and distinct pink skin of Sparkle look very similar to the giant ogre seen in "The Enchiridion!"
A baby similar to him appears in "The Prince Who Wanted Everything."
In the season 7 finale "Reboot," he is now an adult. He is seen with a stubble beard.
Sparkle is shown to have some understanding of his surroundings as he listened to BMO's instructions on two occasions and carried them out without protests. He was also the one who replaced BMO's batteries correctly back into the compartment after BMO had taken them out due to them being wet. Sparkle is incapable of speaking and instead gurgles, giggles, shrieks and huff-and-puffs to communicate.
And though he is capable of crawling, he didn't appear to mind being dragged hand and foot, by BMO, through the forest. However, in "Reboot," ever since he grew up, he now speaks, but in third person like Susan Strong. He is also a horse whisperer.