What Tanya and Simsalabeam have said is mostly correct. However, it is not common to say "get the breakfast/lunch/dinner." Usually it is just "get breakfast/lunch/supper," without the "the." The only time "the" would commonly be used is if you're referring to a meal in a package or container and you're going to physically pick it up and move it.

Someone gets the breakfast. Usually it is a parent who gets it from the kitchen and gives it to the children at the table. Supper is a different meal (supper vs tea vs dinner), but someone will get it (collect it) from the kitchen and put it on the dining table.

I think it should be "Someone gets the breakfast!" it is an imperative sentence, ask someone todo something. as for breakfast VS supper, breakfast for morning while Supper for evening.

Thank you fot your comment Tanya!

It's a little ambiguous. Either can mean getting/buying the food for the meal, making/cooking the food or going out to eat in a restaurant Any of these 3 meanings are possible.