4:53 PM PT -- Rob just uploaded an image of himself on social media for the first time in over a year, and he's showing off his slimmed-down figure in his Halloween costume alongside Kris Jenner.
It's the only picture Rob has of himself on his entire Instagram page, so this is very rare.
Rob Kardashian's stepping back out into the public eye ... for another one of his sister's birthday parties.
Rob was spotted entering Delilah in WeHo well after 1 AM to celebrate Kendall Jenner’s 24th bday, decked out in an orange hoodie and his signature blue baseball cap. As he walked in, he put his hands around the waist of Kylie's current BFF, Stassie Karanikolaou.