Also imps◊ and quasits◊ from the same game. Both of them are the smallest of devils and demons respectively.
While we're at it, most baby dragons don't look very much better than their adult forms, but are still able to pull this off. Especially blue dragons, for some reason.
Blue dragon wyrmlings◊ have huge eyes, faces that look like they've run face-first into a brick wall, big ears (which no other chromatic dragon has) and nubby horns. They're like spiky blue pugs the size of golden retrievers.
Pseudodragons◊. Also described as having 'the personality of a common housecat'. D'awww, I want one!
Though often hated by most, Flumphs embody this trait. Think of a pancake crossed with an octopus floating around and you've got the idea.
Goblins and Kobolds. Two races of three-foot-tall people whose apparent racial destiny is to be killed by first-level PCs - you have to feel for them a little.
Cutebolds are the logical conclusion of this trope.
The infamous Rust Monster◊ resembles a giant mix of a cockroach and an armadillo, but according to the 5th Edition Monster Manual, they're very docile and friendly creatures that make great pets as long as one has no metal on them. Awwwww...No wonder one was chosen as the mascot for Rusty and Co..
The UrbanMech in BattleTech. A stubby, dome-topped "walking trash can" often compared to R2D2 with a BFG spot-welded onto it, the Urbanmech is short, graceless, unglamorous, slow as molasses in winter, and beloved by many fans for its endearingly stumpy qualities.