Today I provide the information below for your enlightenment, my dear reader;) I will resume posting useless information tomorrow.
To get a fake smile when taken a picture, you can say cheese. When somebody sneezes, you can say bless you.
In China, at least in the region where I am from, you say 茄子 (eggplant) to produce a fake smile. And you say 百岁 (100 years old) when somebody sneezes, usually to small children.
In Sweden, omellet is used for fake smile production. The Swedish word for cheese won’t do, unfortunately, since it is ost;) My son might have made an attempt at it when he was littler. And prosit is used when somebody sneezes.