Every time that it's a baby's birthday in my house, I bring them to the cake, and they just stand there. the parents don't throw them up in the air and they become a toddler. They just stand there for hours and hours on end. Has this happened to anyone else?

Yes, this has happend to me. It helps if both parents are there and you may need to try more than once. I don't know why it does this but sometimes it just wont let your babies grow up.

Oh I think I know what might be happening but maybe not. Sometimes if a baby is brought to the cake everyone in the household will have a thing saying "Watch Grow Up" or something like that, and If they have a whole list of other things they're doing before the watch grow up the parent won't throw them up in the air before everyone who wants to watch is watching. If this is the reason you can always cancel the interaction.

it is a glith