A chicks vag and asshole combination package makes an exclamation point (!). Notice the line (vag) and dot (anus) and separation of the two entities (taint).
The unspoken rule that when using exclamation marks, you must always use either one or three exclamation marks in a row. Two or four are not allowed, because they look wrong.
Girlfriend (texting): the new twilight movie is out!! lets go!!!!
Boyfriend: no. you just broke the exclamation mark rule