I remember reading a couple years ago an article in Dragon about the rules for playing characters smaller than small in D&D 4th edition. The article also came with an adventure for such characters, or had an accompanying article in the same month's Dungeon issue, if I'm remembering correctly. I also think that it was pre-essentials, though I could be mistaken in that regard. Does anyone know which issue that is?
The size of both PCs, NPCs, and Monsters affects both size and reach.
Creatures smaller or larger than Medium have special rules relating to position and attacking.
Tiny: Four individual Tiny creatures can fit in a square, but a swarm of Tiny creatures might consist of hundreds, or even thousands, of them in a square. Most Tiny creatures can’t attack, and if they can, they can’t attack adjacent targets. They can attack only targets in the space they occupy. They can enter and end their turn in a larger creature’s space.
Four individual Tiny creatures can fit in a square. More can fit if the creatures are a swarm.
Small: Small creatures occupy the same amount of space as Medium creatures. However, Small creatures cannot use two-handed weapons. If a one-handed weapon can be used two-handed for extra damage, a Small creature must use it two-handed and does not do extra damage.
Large, Huge, and Gargantuan: Very large creatures take up more than 1 square. For example, an ogre takes up a space 2 squares by 2 squares. Most Large and larger creatures have melee reach greater than 1 square—that is, they can make melee attacks against creatures that aren’t adjacent to them. A creature’s basic body shape usually determines its reach—a Large ogre has a reach of 2, but a Large horse has a reach of 1.
The Pixie, a Tiny PC race of HotF, has special rules:
Pixies receive the following racial traits.
Speak with Beasts: You can communicate with natural beasts and fey beasts
Wee Warrior: You have a reach of 1, rather than the reach of 0 that is typical for a Tiny creature. You also take a -5 penalty to Strength checks to break or force open objects. When wielding a weapon of your size, you follow the same rules that Small creatures do.
Pixie Magic: Pixies gain pixie dust and shrink as encounter powers.
I don't know about Dragon issues, but I know that Heroes of the Feywild contained tiny-size pixies as a playable race. The rules for being tiny in general is contained there, either in the pixie race description or a nearby sidebar.