Just wondering, if I ice a cake with whipped icing, does the cake NEED to be refrigerated after it is complete? or can it sit out overnight? Thanks!!

What do mean by 'whipped icing'? Do you mean whipped cream? If you're using whipped cream, yes it needs to be refridgerated.

Whipped Icing as in homemade icing made with whipping cream, powdered sugar, meringue powder, etc...

Yes, real Whipped Cream MUST be refrigerated.

Something like Rich's Bettercream does not.

Just wanted to be sure. Thank you! I very much appreciate it!