Imagine Person A falls asleep in Person B’s lap and Person B has a conversation with someone else while stroking Person A’s hair as if they were a sleeping cat.

http://otp-imagines-cult.tumblr.com/post/140993109687/otp-imagines-cult-imagine-person-a-falls-asleep

This works for any less-than-wholesome pairing (Rylan/Ion, Scorpius/Dark!Esmeralda, etc, etc), but my current thought is regarding A = Sparrow, B = Frost, with the "someone else" (C) being Octavian.