This MLP papercraft is designed by RocketmanTan. Smarty Pants is Twilight Sparkle's old doll from when she was the Cutie Mark Crusaders' age, which is introduced in the episode Lesson Zero. According to Twilight, Smarty Pants comes with a notebook and quill.
When unable to find and solve a "friendship problem" to relate to Princess Celestia, Twilight exclaims that she is going to create one herself. She takes Smarty Pants out of a blue and gold chest in the library and presents it to the Cutie Mark Crusaders, trying to provoke an argument between the fillies that she can solve by emphasizing the importance of sharing.
However, her plan goes awry when the Crusaders turn out to be unenthusiastic about the ragged old doll. Twilight enchants the doll with a "want it, need it" spell, which makes the Cutie Mark Crusaders fight over who gets to play with it, much to Twilight's delight. However, she doesn't manage to break up their fight, and asks Big Macintosh, who was passing by, for assistance. He retrieves the doll, but falls under the spell and takes it for himself, eventually causing a mob of Ponyville's citizens to desire and fight over the doll.
The doll is abandoned by most of the ponies when Princess Celestia intervenes and lifts the spell, but Big Macintosh, showing a genuine want for the doll, runs off with it. In Ponyville Confidential, a picture of him cuddling the toy appears in a Gabby Gums article.
You can download this my little pony papercraft from here: My Little Pony - Smarty Pants Doll Free Papercraft Download