Bonnie Somerville stretches, making her shirt ride up to expose her belly button. This happens at around 27:14 of the show The O.C. Season 1 Episode 10 ‘The Perfect Couple’.
Backup:
https://www.imagebam.com/view/MEWWZLH
https://www.imagebam.com/view/MEWWZM1
https://www.imagebam.com/view/MEWWZM3
https://www.imagebam.com/view/MEWWZM6
https://www.imagebam.com/view/MEWWZM9