Code - effect:

Happy - everyone gets happy
Hungry - everyone get very hungry
Practice - acts are better trained
Fame - act become more famous
Sad - everyone gets sad
Cash - $10,000 falls from the sky

there is a cheat to get all your acts at once, and another to get a huge crowd of people to come into your circus, but I can't remember them.

Also if you enter a cheat and keep hitting return, It'll keep doing it - i.e. 10, 20, 30 thousand