You mean get plantsism. Yes it's a sickness! You can get it by spraying plants that have bugs.... Lot's and lot's of spraying!
You cannot make a sim nude in Sims Castaway.
You can not make a Sim anorexic.
If your Two sims are in Romance level (You know this if your sims can Make out) get both of your sims to relax in Bed by clicking on the bed and press Relax. Make sure both of your sims to do it. Then click on the sims you want to Woo Hoo with and press Woo Hoo or Try to have a Baby
Check out mod the sims
You can't.