I got all the secrets!!!!
Kill over 2000 enemies will reveal all of them: # of lives, stage selection, auto punch (last secret, why?), color for all five characters (Cody, guy, Hagger, Z-Cody, Z-Guy) and 2 additional characters (Z-Cody and Z-Guy).
Using Z-Cody and Z-Guy are funny. They are from Alpha series and look funny. They are very powerful and faster than normal three. I love it <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0">