Coulson’s latest mission is a real drag. Agents of S.H.I.E.L.D. star Clark Gregg slips into his finest stewardess duds for an unforgettable -- and, honestly, really impressive -- performance of Britney Spears’ “Toxic” on Thursday’s episode of Lip Sync Battle (Spike TV, 10/9c). Between his shimmying, the use of props and all that hairography, you have to wonder […]