No, it isn't Halloween, but there are two new masks that you can now outfit your in-game avatar with in FarmVille, with both being available in the new Mardi Gras limited edition item theme. Unfortunately, if you want to dress your avatar up for the party, you'll need to spend just a bit of Farm Cash, as both of these masks are premium.
Both of these masks, appropriately named Mardi Gras Mask I and Mardi Gras Mask II, cost 5 Farm Cash each, and will reward your with 175 experience points for purchasing them. Note that if you purchase one, and your avatar was currently wearing some sort of costume, you will be reverted back to a normal shirt and pants, so you'll need to customize the rest of your appearance to go along with this new mask.
I personally went with a Purple Blouse and Purple Overalls to carry on the theme (as Mardi Gras is traditionally filled with shades of purple, gold, and green), but you're more than welcome to go with any combination that you'd like (or have available via the items you've previously purchased).
Both of these masks will be available in the game for the next two weeks, but if you want to get the most use out of them, your best bet would be to purchase them sooner, rather than later, to make the most of the occasion.
Which of these masks do you like better? Did you purchase one for your avatar? Let us know in the comments.