MorphVOX Junior is a totally free variant of the famous program
MorphVox, whose aim is practically the same. It can modify, change and alter your voice so you sound different, and totally unrecognizable.
From MorphVOX Junior you can make your voice sound like a man, woman or child. You can also add different sound effects that can be used as you like.
MorphVOX Junior can be used from the usual instant messaging programs, or Internet telephony (VoIP), continually altering your voice to make it different, more original and funny.