From Nookipedia, the Animal Crossing wiki
Peppy villagers are female characters who are incessantly friendly and excitable, making them very quick to apologize for anything they regret doing, even if they had not done anything particularly wrong. They account their hyperactivity to candy consumption, although the link between sugar intake and energetic behavior is disproven.
They speak with chipper, bouncy voices and enjoy cheering when talking with players and other villagers; they are rarely discouraged from doing anything. They come out of their homes often. They usually go to sleep at 2:30 AM and wake up at 7:00 AM, always excited to see the player. They have short attention spans and wild imaginations. They often say stereotypical peppy words and phrases like "omigosh!!!" and "like" (as in, "That is, like, so cool!"). When they are describing certain things, they often use "SOOOO" and "totally!". They have an ambition to be popular or famous, claiming letters sent by the player as "fan mail" and are jealous when the player has rumors made about them claiming it to be their job.
They find it easy to get along with other villagers, but may become the center of jokes and gossip created by snooty and cranky villagers, and when either of two are rude, peppy villagers are rude back to them. They get along with normal, snooty, lazy and jock villagers, who naturally avoid making rude comments and share similar lifestyles with them, such as kindness with normal villagers, food with lazy villagers, activities with jock villagers. and typical 'girly' discussions with snooty villagers. They do not hesitate to talk to snooty and cranky villagers, but may sometimes annoy them with their conflicting habits, such as jumpiness, which conflicts with the cranky/snooty "refined" stature.
 Peppy villagers