Plan B: Corporal Punishment - S4-E2
Continuity mistake: Black Adder shoots the pigeon, and the feathers fly everywhere. One feather lands on Black Adder, just above his ear. In the next shot, the feather has moved up, on the other side of his side-part, towards the top of his head.
Answer: According to the IMDB.com's quote page for Blackadder The Third, it's "Aahhhhh. Hot potato, orchestra stalls, Puck will make amends. Owwwwww."