Little Boy is a general name for several characters encountered by Nova in various games.
Happy Wheels[]
"Little boy, come back!"
In Nova's Happy Wheels series, his favorite playable character is the Irresponsible Dad, a man on a bike with a small boy in a seat on the back. The little boy is often abused and killed for Nova's amusement, such as catapulting him from his seat into traps and weapons, and is sometimes used as a last-ditch effort to reach the finish line.
Tri-Mountain Survival[]
"... now, I'm sending you in the water!"
The little boy in Tri-Mountain was a part of the More Creeps and Weirdos mod for Minecraft and made frequent appearances throughout the series. Briefly, Nova aimed to keep the little boy as something of a pet, but he quickly got sick of the boy's cries of "I'm scared!" and "Where's my Lolliman?" and decided to get rid of him. This was proven to be easier said than done, because after throwing him into a mountain, dropping him through a hole in the ice and various other methods, the little boy kept coming back to him until Nova put him into a TF2 teleporter and he was finally gone for good. Then, nearing the end of the series, the little boy appeared again, causing Nova to throw him into a pool of lava while saying "Burn in hell, little boy!"