Gimme Shelter: Outtakes (2000)

When Mick Jagger and Keith Richards are on the studio after mixing 'Little Queenie,' a tired Keith Richards is stretching on a chair and this causes his t-shirt to ride up exposing a good portion of his stomach, and we see Mick Jagger take the opportunity to slap his bandmate's midriff with his entire palm playfully, however the slap is very real and loud, and we hear Keith Richards moaning in genuine pain immediately after.