Why is Simon Cowell hugging a Teletubby?

Four familiar colourful characters made it through to the Britain's Got Talent (BGT) semi-final during the last audition show of the series.

In a surprise, Tinky Winky, Dipsy, Laa-Laa and Po, otherwise known as the Teletubbies appeared onstage to perform in front of the judges.

As Ant and Dec looked on excitedly, Judge Amanda Holden said "We don't need to ask who you are. But who are you?"

Then it was revealed that fellow judge Simon Cowell was once a big part of their success.

Cowell, who is famous in the music industry, signed stars such as Leona Lewis, Little Mix, James Arthur and Olly Murs. But he's also responsible for the Teletubbies having chart success too.

Teletubbies Say Eh-oh - a remixed version of their series theme tune - got to number one back in 1997! It was also in the chart's top 100 for 41 weeks!!

However the four colourful characters with aerials on their heads decided on a different track for their audition, performing Beyonce's iconic Single Ladies dance, before inviting Simon to join them on stage for a hug.

"I felt emotional because we had a lot of success together," said Simon. "I've missed you so much.

The judges sent the Teletubbies through to the semi finals, the first of which starts on Monday night with several acts announced for the first live show.

London Community Gospel Choir will appear in Monday's semi-final, their medley of Love Train by The O'Jays and Anytime You Need a Friend by Mariah Carey received a standing ovation by the judges following their audition.

Meanwhile, one of the youngest in Monday's semi-final is 13-year-old Jamie, who performs a ventriloquism act with his puppet Chuck. The oldest to perform will be 77-year-old singer, Mel Day, after wowing the judges with his vocal performance during his audition.

Born to Perform, who went through thanks to David Walliams' Golden Buzzer, will also appear on Monday night's show.

The dance group is for people with disabilities. Their audition of You Can't Stop the Beat from Hairspray also brought the judges to their feet as they applauded.

Also appearing in the semi-final is impersonator Suzi Wild, who did impressions of the Queen during her first audition, along with the Witch who will be back for Monday's semi-final.

The Witch is one of the most mysterious acts in BGT this year and their performance had Amanda Holden screaming in fear - while co-judge Alesha Dixon had to run from her seat because she was so scared.

Britain's Got Talent is on every day this week at 8pm on ITV.

Who are you looking forward to seeing in the BGT semi-finals, let us know in the comments.