In this evening's audition show we saw Krystyna and her hypno-dog Princess put audience members and hosts Ant and Dec to sleep.
She then went on to hypnotise Simon Cowell making him fall to sleep at his desk.
"It's almost like your brain tells you to do something which you shouldn't be doing but you just go along with it," Simon recalled. "The next thing is, you've actually fallen asleep.
"I always said I wanted to find a cat that could play the guitar. I think we've done pretty well finding a dog that can hypnotise people! I just want to own the dog. I could literally rule the world with this dog because all it does is stare at you and you do whatever it wants."
As well as falling to sleep on stage, Ant and Dec were tricked into forgetting the Number 7.
"For everything else we were perfectly all right apart from when we tried to recall the number seven," Dec explained. "It just wouldn’t come out of our mouths, so it definitely did something."
Alesha Dixon added: "That dog had something special about it, I have to say. Watching Simon fall asleep on the desk, at first I thought he was having us on and then I thought it was real.
"It was a very confusing audition all round, from Ant and Dec being on stage half asleep, it was just weird. You sit there thinking to yourself, ‘Only on this show would something like that happen - Simon Cowell being hypnotised by a dog!’ It’s fantastic."
Even David Walliams was convinced, but reckoned that it may not be Princess who is really the hypnotist.
"We didn’t quite believe he [Simon] had been hypnotised, but on reflection I think he was," David said. "I think it was the woman hypnotising him and the dog was just there. It was a little bit disturbing."
The Britain's Got Talent 2015 auditions continue next weekend on ITV.
Browse pictures of all of tonight's Britain's Got Talent 2015 contestants here...