British actress Emma Thompson gave the cast of a Broadway show a scare when paid them a visit in her creepy Sweeney Todd costume.

The Harry Potter star is preparing to make her New York stage debut in a new production of Sweeney Todd: The Demon Barber Of Fleet Street, playing Mrs. Lovett, the infamous piemaker who helps the title character dispose of his victims.

She has been rehearsing in the same building as the cast of Heathers: The Musical, so Thompson reportedly paid them a visit in full costume.

A source tells New York Post gossip column Page Six, "Thompson has been rehearsing upstairs. And she paid a surprise visit on Thursday to the cast of Heathers to welcome them with some 'freshly baked meat pies' in her full Mrs. Lovett costume... (She said) 'I've brung (sic) you some pies... I don't think you know anyone that's in 'em. But you never know!'"

The Heathers musical, based on Winona Ryder's 1988 film, and Sweeney Todd both open in New York next month (Mar14).