I've been trying to create/run a bakery with one of my Sims for a while now, but no matter what I do, I can't mark his homemade baked goods "for sale." The only things that end up marked "for sale" are the platters that hold the cakes. Even clicking the coolers to mark everything inside them as for sale didn't work; that just did the same thing and made the platters for sale. I also tried toggling the wholesale mode, but the same thing happened on both settings. What gives?

The baked goods themselves won't turn yellow, just the plate. Sims will buy them just fine.

Then they just start taking them away as dinner platters (usually lobster). :/

I'm a little lost. You marked your plates of food for sale and they don't take the food with them when they go to buy it?? If you have the serving plate for sale, yes they will take the whole thing. The food isn't separate from the plate. If you want to sell single serves than you must put single serves into the chiller case.

I mean that they buy the stuff, put it in their pocket/inventory, and then once they leave, some of them hang around to chat with other people and then bring out the serving platter, now with lobster instead of cake or pie, and start serving it to people.

Wow! I wish mine would do that! Interested to know what mod you have in place which allows this.

That is very odd, I have never had a sim serve food they have bought since it goes directly into inventory. What happens if you sell single plates?

I didn't download any mods to cause this.

I haven't sold single plates.

mmm.. strange.. that sounds more like sims 4 than sims 2.
In Sims 2 you mark stuff for sale, people buy it at the register then take it away.
As far as I know, it's not possible to access the inventory in Sims 2, and take stuff out to serve to other people.

You sure you got the right game.

You can access inventory with either the build and buy enabler nod or with boolprop, but that is player directed, sims never in all my ten years dive into their own inventory to serve food.

Yes, I am quite sure I have the right game.