Peeping Big is a giant eyeball monster boss in the Castlevania series. It has appeared as a stronger version of both, a Peeping Eye and a Big Eye, having different properties and attacking methods between its two manifestations.
In Harmony of Dissonance, the Peeping Big appears as a gigantic boss version of the Peeping Eye and serves as the Castle B's counterpart to the Max Slimer. It attacks mainly by floating around the room and swinging its tail, although it also occasionally tucks its tail in, closes its eye (which brings up a barrier that makes it impervious to any form of attack) and bounces around the room for a determined period of time.
When hit, it bounces back, so it's easy to corner it in one side of the room by hitting it repeatedly, making it bounce back and forth until it dies. Alternatively, a well aimed Axe can hit it twice with a single throw.
A giant form of the Big Eye appears as the end boss of the first stage in The Adventure ReBirth. It bounces and rolls around and ejects smaller Big Eyes from its pupil. It can also turn around and fire a large beam.