Plurals, Possessives, and Plural Possessives were not created equal

Jacket and pumps, Banana Republic. Skirt, Club Monaco. Beret, Joe Fresh. Necklace (as a bracelet), mom's vintage. Tights, Hue.

Let's start with a common mistake: "Last weekend, I went to my parent's house." Unless you mean that you have only one parent and would rather not disclose the gender, this is incorrect. Another flawed way would be: "my parents house." It may not be noticeable when speaking, but you should show ownership in your writing, as in "my parents' house."
A recent erroneous trend is using 's to show plurality. I can't even imagine where this comes from, but it breaks my heart every time I read: "We ordered three pizza's." I admit it's partly because I'm lactose intolerant, but if you're gonna rub it in my face, at least be considerate enough to write: "three pizzas." 
Lastly, I would like to address the confusion that comes with the plurals and possessives of last names. Most of my readers are Americans, so the presidential family seems like the perfect guinea pig.

Obama's -  refers to something that pertains to only one of them, such as Obama's policy (Barrack's), or Obama's sartorial choices (Michelle's).
Obamas' - refers to something pertaining to at least two of them or most often, the entire family, such as the Obamas' obvious chemistry (anyone can see that Barrack and Michelle are great together) or the Obamas' dog (Bo belongs to Barack, Michelle, Sasha, and Malia).
Obamas - refers to either Mr. and Mrs. Obama or the family as a whole: The Obamas are the first black presidential couple/family. Other examples include: "Alec is the most successful of the Baldwins" and the ubiquitous "keeping up with the Joneses."

I hope you guys enjoyed this week's grammar installment. It's basic stuff, but we're slowly making our way toward that silly subjunctive and corny conditional clauses.
xoxo,
Grammar Girl.