The thought occured to me that in that episode when the
"Economy Pack" Number Six kept repeating "Number Six!
Number Six! I am Number Six!" during a confrontation that that
ought to have given the game away to the real Number Six. After
all he never cared for going by a number. Should've called his
bluff then and there...

"O.K O.K. let the baby have his bottle.. You're "Number Six" and
I'm... Oh I forget who I am today... Oh well. Nice try. Didn't work.
Bedways rightways. Best we go homeways and all that. Been
nice working with you Number two but there a pint waiting for me
at the Hope and Anchor and we all know how they don't like to be
kept waiting... Be seeing you..."