From Spockologist:
25. Holmes tries to debunk the Santa theory by climbing down the chimney
"My goodness, Holmes! What are you doing up there?"
"I am proving, my dear Watson, that Santa Claus does not exist."
"And how does climbing the chimney prove that, may I ask?"
"Obviously, Watson, if I cannot climb down the chimney, how could a much larger man, carrying a sack of presents, climb down?"
"A sound theory, Holmes, with one exception."
"And what would that be?"
"If you cannot climb down the chimney, how will you get out of it?"
"I'll simply climb back up, of course!"
"Of course. Please do forgive me for asking."
...
"Watson."
"Yes, Holmes?"
"I believe I may be..."
"May be what, Holmes?"
"I may be...stuck."