In Prince Caspian, Reepicheep is the leader of the twelve mice who help to fight against Caspian's Uncle Miraz in the Second Battle of Beruna, near Aslan's How. He and his followers run through the battle and plunge their rapiers into unsuspecting enemy's feet, causing them to fall, after which they are quickly dispatched. Reepicheep is badly wounded in the battle, and he loses his tail. He petitions Aslan afterward to have it restored, as the tail is "the honour and glory of a mouse." Aslan expresses concern about whether the mouse thinks too much of his honour. However, Peepiceek (the second in command of the mice) and the other mice prepare to cut off their own tails to avoid bearing an honour denied to their leader. This solidarity convinces Aslan to restore Reepicheep's tail, apparently not "for the sake of his dignity", as Aslan states, but for the love Reepicheep's people bear him.
In the 2008 film version, Reepicheep led two other mice into Miraz's castle during a mission that did not appear in the book. The three bound and gagged a cat during the operation. Halfway through, they teamed up with Trumpkin the dwarf and opened the gate, allowing Narnian soldiers into the castle.
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