How to Unlock Ape - Monster Rancher 1
Unlocking the Ape monster in Monster Rancher 1 is pretty easy and straight forward. The first thing you need to do is raise a monster capable of finding the Magic Banana item in the Hartville Jungle Expedition which starts on the 2nd week of July each year. If you have a monster that meets the minimum requirements to go on Expeditions then Karn will show up and ask you to come on an Expedition on the date specified. You need a monster that is at least Rank C with 40 fame to get invited to Expeditions in this game.
There are 6 different searchable areas in the Hartville Expedition that you can find the Magic Banana, you'll need high Intelligence and/or Skill to find this item. For more information about where the searchable locations are I strongly recommend you visit Legend Cup's Expedition Maps page. That guide will give you most of the information you need for navigating this Expedition.
Once you find this item you will get a debrief when you return home by Tesca, he'll tell you that you must spoil 2 monsters then use this item in the Combining process. It doesn't matter what type of monster you spoil and combine, so long as they're spoiled the combination will work without any issues.
In order to spoil a monster in this game you should feed them Meat every month and/or Apple Cake items from the Shop. Holly will make a comment at the start of a day when you spoil a monster, she'll only do this once per monster so pay attention incase you miss it!
Also, it'll say "Spoil" in the bottom left at the main "Ranch" screen once a monster is successfully spoiled. This is easy to do so I won't go into too much detail about it, you'll very likely unintentionally spoil all of your monsters by feeding them Meat each month anyway.
Note: Holly says your monster is spoiled before your raising style says "Spoil" in the bottom left. I kept feeding Apple Cake to my monsters until the raising style said "Spoil" then did the combination. I'm not sure if it'll work the other way but you can test it if you'd like.
Once you've spoiled 2 monsters and frozen them at the Lab you'll want to Combine them using the Magic Banana item, as I mentioned earlier. I recommend you save your game before doing this combination just incase you did something wrong. Assuming that you did everything right your Combining will result in an Ape monster for you.
How to Unlock Ape Monsters:
1. Level up a monster enough to get invited to Expeditions
2. Participate in the Hartville Jungle Expedition and find a Magic Banana
3. Spoil 2 monsters by feeding them Meat every month and/or Apple Cakes
4. Combine 2 Spoiled monsters with the Magic Banana item to get an Ape monster