Gandalf keeps Bilbo distracted while someone pushes a stick towards his exposed nose.
OR
Bilbo: "Oh, Santa, I want a barrel of Old Winyards, and I want to see the Lonely Mountain again, and I want a barrel of pipeweed... no TWO barrels... No, a field of pipeweed!... NO! All the pipeweed fields in the Shire!
Gandalf: "I think you've had a bit much..."
OR
Gandalf finds it difficult to stay awake as Bilbo tells him about his experiments with mushrooms and wine.
Bilbo: "And then I planted some of Maggot's 'shrooms and watered them with my father's 1296. They turned into this peculiar pinkish-purple plant. It really wasn't that great, but looks good on the table... I think next I'll try..."