A long, long, time ago, deep in the forest, a stork was carrying a basket containing two tiny blue creatures known as baby Smurfs. They were twins, but one of them was a girl, the other was a boy, and the girl was wearing a black Smurf hat and dress. However, across the way, the stork was struck by lightning. It made a recovery, but the girl Smurf fell into another Smurf Village, not the one the stork was going to. When the stork arrived to the right Village, it realized it was missing a Smurf. However, the oother Smurfs didn't know what he was saying, so they raised the boy Smurf, who became known as Brainy Smurf.
Fast forward to about 100 years after the accident...
Brainy Smurf was sitting in his hut. He only had vague memories of the trip to the village when he was a baby. He still missed his twin, but knew there was no way to get her back. He had nightmares every night, of her falling out of the basket into the forest, but he didn't know where it was. However, one day, someone came up to his hut and knocked on the door. Brainy opened it, and Clumsy, his best friend, was there.
"Happy Smurfday, Brainy!" Clumsy said. Brainy had completely forgotten today was his Smurfday. "Oh, and, wanna hear something kinda funny?"
"Ok, Clumsy."
"There's a new Smurf in the Village. I would go into more detail, but, it's mostly a secret."