People stunned by one detail as Christina Aguilera sings with Sabrina Carpenter

Fans have been left stunned after watching Christina Aguilera's performance with Sabrina Carpenter, with many pointing out a specific detail.

To celebrate the 25th Anniversary of her debut album, titled Christina Aguilera, the 43-year-old visited Spotify's studio in Los Angeles to sing some of her classic songs, which included 'Genie In a Bottle' - a track that has been played more than 445 million times on the streaming platform.

Sabrina Carpenter joined her on the couch towards the end of her studio session, with the 25-year-old admitting she's a huge fan of the 'Say Something' singer.

We'll all be aware that Carpenter is one of the hottest singers on the planet at the moment, having released hit songs 'Espresso' and 'Please, Please Please', along with 'Taste' - which has an epic music video to go alongside it - all in this year alone.

"I'm freaking out!", Carpenter said from the couch. "As I'm sure you already know this, but I just want to like get into a few different things and start off by saying that I think the first time I ever heard your voice was - my mom, thank you to my mother, played me a video of you singing at eight years old, 'A Sunday Kind of love'.

"And that was just like the most inspiring thing for me ever to see as a young girl that wanted to sing but didn't know I could do it at that age at all and definitely couldn't do that... But you were like a child.

"It was the main reason that I started singing and wanted to become a singer. So I'm just so grateful."

Sabrina Carpenter explained how Christina Aguilera was the reason she got into singing (Spotify/Christina Aguilera/YouTube)

The pair then went on to duet 'What a Girl Wants', from Aguilera's first album... queue the haters.

When a snippet of the video got uploaded onto Twitter, users were stunned by one detail - apparently, Aguilera outshone Carpenter.

One user, who posted the video, captioned it: "Everybody a good singer till you gotta go toe to toe with the real deals."

While someone else commented: "I saw an entire discourse last week and people were acting like Sabrina is Whitney Houston level singer like pls."

Christina Aguilera celebrated 25 years since the release of her debut album (Spotify/Christina Aguilera/YouTube)

And a third typed: "Ok because I’m like Sabrina why are you down there ?! LOL This is when you show us that range love !"

But many came to Carpenter's defence, with one pointing out how the two singers have completely different singing styles: "Comparing two different vocal abilities like that is telling everyone you know nothing about music."

And a second tweeted: "Sabrina’s still a great singer this changes nothing."

It was good to see the mutual respect Aguilera and Carpenter had for each other... even if their fans didn't show the same!