Clear tall grass
If you click tall grass with a ground level tool, the grass will change to its "normal" state. This costs no money and will prevent guests from complaining about uncut grass.

Special-Name Guests
Changing a guest's name to one of the following will have the effect listed.

Password - Result:

Richard Tan - Guest will be theif
Tony Day - Guest will be hungry
John Wardley - Guest will think positively
Chris Sawyer - Guest will have multiple photographs taken
Michael Schumacher - Guest will drive go-carts fast
Katie Brayshaw - Guest will wave
Simon Foster - Guest will paint pictures
Damon Hill - Guest will drive go-carts fast
John Bibrough - Guest will increase park rating
Melanie Warn - Guest will be automatically happy
John Mace - Guest will pay double on rides
Mr.Bean - Guest will drive go-carts slow
Richard Branson - Guest will make other guests have a lot of money