Sunny Baudelaire is between the ages of one and two years old through most of the Lemony Snicket books in A Series of Unfortunate Events. She is a remarkable baby in terms of her comprehension and skills, and she is often an important asset to the Baudelaire children despite her age.

Sunny speaks in a version of "baby talk" in which she will spout out a word or two that are comprehensible only to her siblings. These words, however, always contribute important additions or insights to whatever problem the older children are trying to solve. Sunny also comprehends what is needed of her. With her love of biting and her sharp front teeth, for example, she can be useful when items need to be cut or modified.

Sunny has a good ability to rise to the occasion. For example, when she is forced to be Vice Principal Nero's administrative assistant at the Austere Academy because she is too young to attend school, she somehow manages.

Like her older brother and sister, Sunny has a strong moral compass and can sense the difference between good and evil. Although she is very resourceful, because she is also so small, she depends on her brother and sister, even as she often contributes to their survival.