Penn Badgley Replaces Blake Lively With Hilary Duff On The Set Of 'Gossip Girl' (Caution: Kissing Ahead!)

Spotted: H.D. and P.B. sharing a kiss on the NYC set of GG on Wed. For the non-"Gossip Girl" speakers among us, that means Hilary Duff and Penn Badgley were spotted smooching on-set Wednesday. Rest easy — he wasn't cheating on girlfriend/costar Blake Lively, he was just filming a scene with Hilary, who booked a multi-episode guest spot on The CW show earlier this year. According to EW.com, Hilary's character is a Hollywood actress who ends up as Vanessa's (Jessica Szohr) roommate at New York University. From the looks of the photos in our flipbook (click on the image below to see all of 'em!), a love connection between Olivia Burke and Dan Humphrey ensues.

We'll get to the kissing part in a second, but can we take a minute to admire how well-accessorized the pair is? Hil's adorable green purse (which is actually Mulberry's popular summer slouchy bag, the Mitzy hobo) + Penn's Spencer's Gifts-meets-Fred Segal blue watch (which is a little more of the latter — the Nooka Zub Zoo 38 timekeeper retails at about $140) = perfectly complemented hues and clothing.

While we'll have to wait until October to see how this plot unfolds, but we can pretty much speculate what happens now. However, there are a few questions left on our minds: How long will this relationship last (if it is even a "relationship"! God knows Dan's one to have a wondering eye if you'll recall the Georgina incident)? Will this fling make Serena jealous (we're thinking 'duh, of course')? How long until Ms. Movie Star leaves Dan brokenhearted so she can shoot a film in an exotic location?

Tell us what you're hypothesizing about as far as Dan and Olivia's romance in the comments section below!