You only get to host Saturday Night Live for the first time once. We know Kristen Stewart was pretty psyched about it, considering she accidentally dropped the F-bomb (and promptly freaked out about it) during her opening monologue over the weekend. Still, the actress and R29 Shatterbox director nailed the first impression bit, both with her on-point punch lines and the "too cool" riff on the LBD. The maker of her outfit, though, isn't some downtown designer you've never heard of. It's not a one-off thrifted find from a small town somewhere. Nor is it a bespoke garment made by monsieur Karl Lagerfeld. Rather, it's a brand you'll find at your local mall — and probably in your closet. Stylist Tara Swennen shared Stewart's outfit credits on Instagram shortly after the broadcast. And while Chanel and Christian Louboutin were represented, as usual (in terms of Stewart's jewelry and shoes, respectively), the label on the actress' black mini was quite unexpected: Under a YVY mesh skirt, Stewart donned Spanx's Thinstincts slip. Yup, that's right — that Spanx. Of course, we know Spanx makes much more than just shapewear, and that celebrities are as big fans of its non-undies as they are of their smoothing garments. Still, we were pretty psyched to see K.Stew, looking as fly as ever, in a slip that rings in under $100. Now, if you'll excuse us, we have to go spruce up our LBD collection.