To pull someone's chain is considered slang for taking advantage of a person unfairly; to tease or annoy just to see their reaction.
From an obscure source, this is reputed to have been said by a former Mayor of Ottawa, Charlotte Whitton ( March 8, 1896-June 25,1975 ), while in service during her first term, 1951 to 1956 or during her second term, 1960 to 1964.
Whitton was introduced to the (nameless) Mayor of London, England. He was adorned with medals and chains, befitting of his position. She wore a lapel flower.
" There was something fitting about this, wasn't there," asked the London Mayor. "After all, what was Ottawa, a city of 600,000, compared to London, 10 million ?"
Leaning towards her lapel, he purportedly said, " If I sniff your rose, will you blush ?"
Charlotte, the Feisty, replied," And if I pull your chain, will you flush?"
Brevityquest12 (146 words and numbers)