Let the nostalgia wash over you!
The former onscreen father and daughter hugged it out backstage at the actor's Hand To God play on Broadway.
Bob posted the photo on his Instagram on Wednesday, December 23, and wrote:
"We all loved having my beautiful friend Mary Kate Olsen @HandToGodBway last night. Love her so much."
Aww, you guys!!!
The 59-year-old later posted another shot of MK holding a hand puppet to his account: