Youngster David Knight was aiming to impress judges McIntyre, Amanda Holden and David Hasselhoff with his stand-up comedy routine in Birmingham, reports The Sun.
However, when Knight revealed before he had even started his act that Harry Hill was his favourite comedian, McIntyre chose to hit his buzzer, prompting the child to start crying and insist: "I was about to say you were my favourite!"
McIntyre quickly added: "It was a joke - but it wasn't one of my best."
Knight went on to impress the panel with his performance, after which McIntyre admitted: "I'm sorry. You're a star in the making."
Hasselhoff also said: "You are not only the best 9-year-old comedian I have seen, you are the best comedian. You belong on that stage. I've never seen anyone intimidate Michael like that. I love you for it."
McIntyre later said of Knight's reaction: "He had bought a one-way ticket to tears. I thought I was going to have to jump on the stage. The buzzer is so loud! I hope they edit that out - I don't want to see him jumping out of his skin."
The 34-year-old comic also caused another hopeful to storm off the stage after buzzing him out during his audition. The judge added: "He's not the father of the young comedian, is he? That family hates me."