Zooey Deschanel and Joseph Gordon-Levitt are going to kill you with cuteness. (YouTube)

The “500 Days of Summer” co-stars’ duet was posted to Deschanel’s Web site, Hello Giggles. Yes, even the name of the Web site is adorable. The two have known each other for 12 years, Deschanel wrote on the site, since they filmed the movie “Manic” together. The “New Girl” actress called Gordon-Levitt “one of [her] dearest friends.”

While Deschanel is pretty well-known for her band, She & Him, you may not be aware that Gordon-Levitt can sing, as well. We here at Celebritology previously marveled at his Serge Gainsbourg and Kelly Clarkson covers.

Watch the twee-tastic duet below.

(Via Buzzfeed)