I'm making a fall wedding cake with fondant leaves I made on it.
How soon should I add the leaves. I want to have the cake done on Friday eve. because I'm way too busy to work on it before the Sat. AM wedding. I plan on keeping it in the fridge and I dont want the fondant to get mushy or weird. Any Advice?

Will the leaves be ok overnight on the cake in the fridge?

Well it depends on your frig mostly.
Everyone said not to put fondant in the frig. I had a very fancy decorated cake leftover - had a big loopy bow on it. I did put it into the frig for at least a week and guess what? Not a single problem when it came out
Yu could try putting one leaf in the frig overnight and see how it comes out......but I think you will be just fine.

I think i'll try that. Thanks.

Why does the cake need to go in the fridge in the first place?

Cream cheese filling...and its close to 100 degrees here in so cal.