You and Leonard's friends were all heading to San Francisco via train (Sheldon's fault), an eleven hour ride.

You sat next to him and after shenanigans with Howard, Raj and Sheldon, you start feeling sleepy.

Leonard was leaning on the window, doing nothing, just staring out the window until he tenses up in shock and looks over at you leaning on his shoulder.

He blushes and cracks a smile as he leans his head on the top of yours.