He was a famous barber with a wife and child. This man was jealous and in love with his wife. So he knocked Sweeny out and sent him away, while this man planned to say he was dead and woo Sweeny's wife. Sweeny comes back years later with revenge
It's a Sweeney Todd reference. Sweeney Todd was a fictional demonic barber who lived in Fleet Street, London, who slit his customer's throats and gave the corpses to Ms Lovett, who would then make them into meat pies and sell to customers. Here, Pinkie Pie is the one who makes the human-flesh pies for Ms Lovett. Does that help? Btw Sweeney Todd is a Victorian character. Just so you know.