Hollywood loves Halloween!
In one shot, Zac—who completed a rehab stint this past April—hangs onto a candy apple and his pal Brittany. (Don't start playing the couples game here! Britt is dating Teen Wolf's Tyler Hoechlin.)
Derek, whose girlfriend Nina Dobrev did not appear to be part of the festivities, Instagrammed a smiling, happy shot of himself and his famous friends. "Great time last night with great friends," he wrote Friday. "Love this time of year."
Nina's not missing out on all the fall fun, though! Earlier this month, she and her Dancing With the Stars beau stepped out for the first time as a couple at Universal Studios Hollywood's Halloween Horror Nights at the Roosevelt Hotel. Julianne also joined the pair, along with Lily Collins, Selena Gomez, Emile Hirsch, Francesca Eastwood and Beacher's Madhouse founder Jeff Beacher.
So what's next? Let's hope for a young Hollywood group visit to the pumpkin patch or costume previews on Instagram!