Severus caught the slight widening of James' eyes - magnified as it was behind the man's glasses. Gotcha! He gave James a grin and perhaps, what with the triumph and all, it was a bit more vivid than he'd planned.
Then Lily spoke and Severus played up to her McGonagall impersonation, sticking out his thin lower lip in a parody of a hangdog expression. "Not even if it's not mine?" he whinged, in a spot-on impersonation of a grizzling firstie.
Not that his impersonation lasted once Lily mentioned cobbler. "Did someone say the C-word?" he grinned. "You do mean the apple sort? Granny Smiths, and brown sugar, and all the proper spices? Cinnamonnutmegclovesallspiceginger?" he asked all in one breath, his whole expression alight with anticipation.