OpenAI Gym consists of many different environments and many are added to it by its active contributing community. To get a list of all the existing environments, you can run this simple code (taken from https://github.com/openai/gym):

from gym import envs
env_ids = [spec.id for spec in envs.registry.all()]
print("Total Number of environments are", len(env_ids))
for env_id in sorted(env_ids):
    print(env_id)

At present, OpenAI Gym has 777 environments in total. Here is the image of Pac-Man using the same random agent as earlier: