Cinnamon cookies are a happy smell.......
I smell like soap.

Does that count as a happy smell? (after work, I'll be smelling more like teriyaki sauce and noodles.)
But seriously, I find that just smelling very very clean is the best thing. Some people has troubles with perfumes and scented things, and giving out headaches is not something clowns usually do....
And lots of deoderant. Costumes are hot. Especially if they're polyester. And body oder is, again, not a pleasant thing.
But I still say cinnamon cookies are a happy smell................