My faves...as much a reflection of the shows than the catchphrases themselves.
"And now for something completely different..."
"Calm down, calm down."
"He's from Barcelona"
"I didn't get where I am today..."
"I don't believe it"
"My arse"
"No, no, no, no... yes"
"Titter ye not"
"You silly moo,"
"You wouldn't let it lie"