Robin Goodfellow, also known as Puck, was often found in Celtic mythology and English folklore. Puck was a Pagan(pre-Christian) nature spirit, or a "woodwose". Robin Goodfellow is a trickster figure and played many tricks on people in many folktales and other stories. The use of Puck, in The Midsummer Nights Dream, allowed the commoners in the audience of the time to relate to the mischieveous character.
Puck would do minor housework for people if he wanted to, but he could also undo the work he did and wreak havoc on them. Some knavish things Puck would do was take the shape of animals, blow out candles to kiss the girls in the darkness, make them fall out of bed onto the cold floor, tattle secrets, and switch babies in cradles with elflings. Calling Puck, "Goodfellow", was a way to hopefully avoid the devious tricks that Puck would play.