Anyone have an idea what the balls in the cake are made out of?  Is it rolled fondant?

Fondant is a good choice or they could be cake balls/ pops

There are so many and such different sizes, I am guessing some of them are fondant or modeling chocolate, some maybe rice crispy treats covered in fondant and the largest ones appear to have a little nipple in the center, as though they are meringues.

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Good ideas Sandra Since I don’t use meringue Or modeling chocolate They didn’t occur to me I just noticed the little teddy bears—especially the head at the bottom next to the tongs That’s guitar a baby shower — or maybe a 1st B day:)

It is an adorable cake.  Actually, it has so many balls, I didn't even notice the small Teddies.  Maybe a few less balls.

And since some of them are silver & gold I would thik them must be either RKT &/or fondant.

Definitely either fondant or modeling chocolate.

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Some of them, the larger ones, may also be made from gelatin bubbles.

I don’t think any of these “bubbles”/“balls” are gelatine Sandra. If you enlarge the picture, and look closely, there all too big and firm to be gelatine. Gelatine balls are almost see through, and very fine in texture.  I agree with kakeladi, either all fondant, or rct’s covered in fondant. A possibility of modelling chocolate, but most likely not. With this many bubbles/balls, modelling chocolate would get pricey. 

cake balls would be nice edible items on the cake.  For large balls, fondant pressed around foam balls are pretty light & handy to use.

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