Cheat List:
Rename a guest with the name as noted below to get the desired result.

Chris Sawyer -- Will take pictures of your rides
Simon Foster -- Will paint pictures of your rides
Melanie Warn -- Increases the guest to completely happy
Katie Brayshaw -- Will wave to everyone she meets
John Wardley -- Says "Wow!" when he sees (or is on) a good coaster
Damon Hill -- Races around twice as fast on the Go Karts
Michael Schumacher -- Works the same as Damon Hill, but a little faster (and NO you can't race Damon and Michael!)
Mr Bean -- Will drive VERY slowly on the Go Karts