While Mirza wowed the crowds with his Michael Jackson impersonation, Singh wandered on stage, broom in hand, on the pretence of sweeping the floor.
Signature gave Jackson hit 'Thriller' a Bollywood edge, which judges agreed was one of the ITV1 show's most original performances.
"You are two ordinary guys doing ordinary day jobs and by nights you do this crazy, crazy act," The Sun quoted judge Piers Morgan, as saying.
Simon Cowell said: "This is one of the best acts because what you have is something so important - you have originality."