After six years on the show, Alesha says there's "never a dull moment" behind the scenes.
The singer returned alongside Simon Cowell, David Walliams and Amanda Holden for the 2019 series this year.
Alesha said: "Simon misbehaves. He’s quite mischievous and he’s always on the wind-up.
"There’s never a dull moment because he’s always looking for that little thing that’s going to make you laugh or trip you up. It’s like being back at school. He tries to draw you into his strange world."
And it's not just Simon on the wind up.
Alesha added: "It just feels like the gift that keeps on giving, because it always gets better – and Simon’s much calmer this year!
"David loves to wind him up and usually Simon would tell him off, but this year he’s more laid-back in terms of letting him get on with it.
"I think he’s given up telling him off!
"I’ve seen Simon doing things I never thought I’d see. We have an end-of-term party in the judges’ dressing room and I look round to see Simon and David dancing!"
Speaking to Star magazine, Alesha revealed how the panel took the tube to the auditions for during filming recently.
"Amanda and I were in our TV outfits and then we had David dancing around one of the poles, we were getting the strangest looks," she spilled.
Meanwhile, Alesha promised that the show was still continuing to find amazing new acts after more than a decade on air.
"Usually we’re all a bit nervous about finding enough talent, but we were genuinely spoilt," she said. "Every year we can make a prediction about who’s going to win, but this year we couldn’t. "
Britain's Got Talent airs on ITV.