Cat from is a major one.
Cat and Girl The eponymous character of . Complete with Hanna Is Not a Boy's Name Gender-Blender Name, natch. Notably, he is seen in an official guest strip making a face more commonly seen on SpongeBob SquarePants ("FREEEEEE"), doesn't narrate the comic because he's too hyper, and has a Tall, Dark and Snarky sidekick/ Heterosexual Life Partner who does narrate (and is more than One Head Taller than Hanna). Hanna is not quite 5'3", has almost-fluorescent red hair, often dresses fairly colourfully, is quite the Motor Mouth, and is Older Than He Looks: as his bio says, he's "best described as an overly enthusiastic, obnoxious child in the body of a twenty four year old man." Except not exactly the body of a twenty four year old man, because he looks so young that nobody ever believes he's an adult.
Kazuki from Kenshiro no Tabi, who upon imbibing triple-sweetened strawberry-milk released enough energy to create a nuclear explosion.
Rocky from . A skinny sugar addict smartmouth, Rocky's boundless energy combined with poor impulse control regularly gets him into trouble.
Lackadaisy Taisei from does fit the "hyperactive", "cheerful", and "loud" part, but he's not exactly small.
Sakana T-Bob from , described in an early bio as "the living embodiment of caffeine."
Something Positive Pretty much deconstructed in . Fritz is five-foot-nothing, The Quick and Dirty Life of Fritz Fargo very emotional, very loud (he's a vocalist in a rock band), and very, very energetic. He also has a Heterosexual Life Partner who's One Head Taller than him and twice as broad as he is, Anime Hair, a missing tooth that makes him look rather childish... and a really serious cocaine habit, which is why he's so hyperactive.
Selby the spaniel from .
Woods For The Trees