R.O.B., one of Nintendo's iconic characters, is hidden in the Curiosity Shop. However, you can't see him if you enter from the front entrance. You have to access Kafei's Hideout, which is only accessible on Day 2 if you put Anju's letter in the mailbox, then go inside while Kafei is retrieving the letter. Inside, Kafei will show you a peep hole that looks into the back of the Curiosity Shop. If you pan the camera to the right, you'll see R.O.B. sitting on a shelf.