The gorilla is an animal that can be found in a sealed valley behind the jungle town. Although it can be purchased for 1,000 tickets, it is much more cost effective to catch one or complete the gorilla cage quest.
Enter the Gorilla area in the Jungle biome, which you can enter by having a level 5 pet with Smash or by having a level 6 pet with Climb (Although, this is currently bugged since pets of all levels with the Climb ability can enter)(*patched*). You can also go to the top of the toucan tree in the jungle to fly there.
Once inside, you will be met with a daily quest giver to your left and the Gorilla King ahead of you, banana trees scattered around.
The Gorilla King gives you a free Gorilla egg when you give him 250 bananas