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 There have been a couple of pixie vampire builds (usually referred to as "mosquito" builds) posted on the forums that have been refluffed as both a Metroid and a stirge.

   I have a shape-shifting Fey crow spirit from the Feywild who worships the Raven Queen - he saw her flying through the Feywild one day, fell instantly in lust and chased after her, hitting on her. She led him on a merry chase for miles and left him stranded in the material world. He spends most of his time in combat as a crow, whirling about his opponents and slashing them with his claws. Out of combat, he sits on the shoulder of the party's spellcasters, pretending to be a familiar. He shares much of the same personality traits and habits of a crow: he's loud, raucous, intensely curious, greedy, sarcastic...and occasionally likes to snack on dead things.
( Oh, and hes a pixie predacharger druid. Pixies can fly and are Tiny and druids can wildshape into animals of their own size. Thus I have a druid who can change into an actual flying bird without blowing a utility power to do so. And being able to charge in three dimensions (and through opponents' spaces) offers a number of interesting tactical possibilities.)

I've also seen a couple of swarm druids who were fluffed as being sentient swarms of bugs. One particularly interesting one was a magitech swarm of nanites who arranged themselves into the forms of other creatures (changeling racial ability)...

 In 3.5 I had a warforged druid who was refluffed as a genius loci - a swamp that had been the site of so many battles over the ages that it had absorbed the life energy of those who'd died there and gained sentience. Tired of being despoiled by humans, it grew a tree up through the remains of a suit of armor, magically animating it by imbuing it with a spark of its vitality. The now sentient plant-man armed itself from the multitude of ancient gear buried in its soil and set out to wreak vengeance on the orc horde that had been the latest vermin to defile it.

 Ever read the Micronauts comics? The character of Bug is perfect for a 4E thri-kreen monk - the guy's all about bouncing around in combat and his main weapon is a blast-staff that shoots beams of energy.

 One of my warlocks, Harrow, is his own pact patron... One day, in a bad mood, he ATE a Tinkerbelle-style fairy who had the misfortune of asking him what was wrong - just grabbed her out of the air and stuffed her in his mouth. Being immortal, the now-digested fairy reformed as a sort of symbiotic second central nervous system inside of him, and her now-mind-rippingly-insane consciousness currently shares his headspace. He often argues with himself in two different voices at once and sometimes falls to the ground twitching and foaming at the mouth as they fight for control of his body. His physical body keeps her consciousness from dissipating and her magic fuels his Fey pact powers. A number of his powers are occasionally refluffed as the green glowing image of the fairy coming out of his body and doing things.

Ah, yes, almost forgot.

Rogue-Fey Pact Warlock Hybrid=Ninja.