To get the ape you need a magic banana which can be found in an adventure with Karn in the jungle. In the jungle, look for the place where the kings once lived. Have your monster check it out and eventually you'll find the banana. Once you have it you now need to have two spoiled monsters. The easiest way to spoil them is give them meat each month and let them rest all month. After you've spoiled two of them, freeze them both, the combine them with the magic banana. It will say the combination will create an Asfar or a Boxer, but because of the magic banana it will create an ape. Be warned: this monster is extremely lazy.