Both Robin Goodfellow and the Puck are attendant to the Queen of Faerie, acting as both fool and manservant. In outward appearance they are very similar, covered in soft brown fur, head too large and limbs too long. Robin delights in wordplay and prances and cartwheels for his queen’s, and his own, amusement. Tom is fond of Robin Goodfellow as the fay always tried to cheer him up whenever he felt lonely or homesick.
Puck, whilst looking a lot like Robin Goodfellow, is a very different creature. He might indulge in word games, but will bite you or drop something on your head while you were thinking of a response. His pranks involve pain and suffering and he crawls on hands and feet like a predator. Many a mortal has run afoul of Puck by thinking he is as kind and funny as Robin Goodfellow.
Is Robin Goodfellow the most famous fairy? Possibly. He was certainly the first fay I named for The Fey Man. In fact, as Robin Goodfellow is often known also as the Puck, he directly suggested the idea that fay have two faces: one for summer, one for winter.