Certain badges may appear next to someone's forum posts and on their user profile page. They are awarded automatically when the relevant requirements are met. The meanings are:

Badge Meaning
Over 1300 balls saved in official levels.
Has spent more than four days solid in the game.
Has completed OCD on all official levels.
You are Ron or Kyle.
An author, moderator or contributor on this site.
Author of a World of Goo level or mod.
Naughty, naughty.

Coming Soon:
Architect of the world's highest tower.
Architect of one of the world's 5 highest towers.
Architect of one of the world's 25 highest towers.
Most balls saved on at least one level on the leaderboard.
Least moves on at least one level on the leaderboard.
Fastest time on at least one level on the leaderboard.

These badges were created by Jamerz.