I was thinking of a mod idea. I don't know if this is already a mod, but if you view the links below, you will see 4 removed mobs. I was thinking somebody could make a mod that adds them again since I never played the version that these mobs were in. It would be good if the mod was made by somebody who actually saw these mobs. Thanks!
I don't know of any mods that do this, there are probably many, but I do have a program called Minecraft Version Changer. Pretty self explanatory, Its a very easy to use prgram that will change you .minecraft into any previous or current version of minecraft. You can save backups and all that stuff so you dont screw anything up aswell. So go download that.
http://www.minecraftwiki.net/wiki/Beast_Boy
http://www.minecraftwiki.net/wiki/Black_Steve
http://www.minecraftwiki.net/wiki/Rana
http://www.minecraftwiki.net/wiki/Steve_(Mob)
The mod is found at:
http://www.planetminecraft.com/mod/dock-mod-145-adds-old-mobs-by-dock/