Have you seen "Hey room you can create custom emotions by editing the emote_user.dat file" or strange emotions in a yahoo chat room?
Wonder how to make your own emotions for yahoo! messenger chat?

emote_user.dat (custom emotions)
 

To make your own custom emotions go to the folder:
C:\Program Files\Yahoo!\Messenger\ on your hard drive and open the file emote_user.dat with notepad.

type a new emotion at the bottom of the file in this format:
EmotionName\Text for room emote\Text for single user emote.

• include \ between each part

• Put %s where you want the person your emoting's name.

  Example:
  
  example\hi everybody\hi %s
  typing this makes a new emotion called "example" and makes the messages appear like this in the chat window:
  
  

   

• remember to save your changes to emote_user.dat! (file->save)

• you will need to close and reopen any chat room you had open for your emotion to appear.

• this does not work for the java based chat.

• to emote the whole room don't select anyone

• to emote one person select their ID from the list to the right