Name changing ceremony

A name changing ceremony is a ceremony that takes place when a Clan Leader decides to give a Clan cat a new name. This is usually done when the cat's old name does not suit him/her anymore, or because of an injury.

Process
When a cat's name no longer portrays who they are, a Clan leader can perform this ceremony to change it to a new name. Normally, the name is changed from the result of an injury, for example, when Sparrowpelt lost half of his tail, he was re-named Halftail. However, sometimes it is changed when the cat has been named incorrectly and the leader wants to rectify this mistake (i.e. Brightheart).

Ceremony
The leader calls a Clan Meeting, and performs the change with the following words:

"Spirits of StarClan, you know every cat by name. I ask you now to take away the name from the cat you see before you, for it no longer stands for what he/she is. By my authority as Clan leader, and with the approval of our warrior ancestors, I give this cat a new name. From this moment on he/she will be known as (new name), for (description of the reason)." 

Cats who Have Changed Their Names in the Warriors Series
It is also likely that Deadfoot, Stumpytail, Ratscar, Kinktail, and Tornear are also results of name changes, as they both refer to injuries obviously received after birth. However, this has never been confirmed and their previous names have never been said.

Other Information
A cat can also request a name change, if they would like their name or someone else's name to be changed, such as Cloudtail asking Firestar to change Lostface's name, or Rainflower requesting her son's name, Stormkit, to be changed to Crookedkit.