The band performed on the show finale last night and were joined by judge Robbie for a special performance of Everything Changes.
And Robbie made sure to show his appreciation as he rejoined the band he left 23 years ago by fondling Mark’s package as they performed.
Reaching across while they were live on stage, the cheeky judge gave Mark’s bits a squeeze – leaving Mark in hysterics.
The reunion, which was first revealed by The Sun back in October, delighted fans and the crowd watching the show’s finale.
The crowd at Wembley were up on their feet when Robbie jumped up to join his former bandmates.
Afterwards, Robbie told Dermot O’Leary: “It always feels like home!”
Gary Barlow affectionately added: “I think about him a lot.”
But he stayed tight lipped over whether Robbie be joining the group on their 30th anniversary tour next year.
Robbie had previously said he was keen to take part in the reunion in some capacity.