As I'm trying to frost a sheet cake I'm noticing what appears to be air bubbles in my buttercream which is making it hard to get the frosting to look smooth - any on ever had this happen? What did I do wrong?

People have given a lot of tips on here before about this problem. One that I've found helpful is to run my rubber scraper through the frosting before I start putting it on the cake -- kind of swipe the frosting against the side of the bowl with the scraper.

I've found it helpful to add a drop or two of water to the buttercream and slowly cream it with a paddle mixer if I find air bubbles in it. Whipping it too fast while mixing creates air bubbles. If you've already frosted the cake, try dipping your spatula, bench scraper or whatever you're using in warm water and smoothing the buttercream with that.