The Spanish version of the tooth fairy is a cute little mouse called 'El Ratón Perez', and this small museum close to Sol takes you into a recreation of his home. Entry is by guided tour and the commentary is only in Spanish, but it's still worth a visit as you'll see his secret door, a layout of his home inside a biscuit tin and all manner of little artefacts. Entrance is via the passageway signed 'Centro Comercial Arenal 8'.