The comedy duo appeared on the hit Saturday morning show from 1987 until 1993 when it ended, before moving on to it's successor, Live and Kicking, until 1997.
More than 20 years on, the pair were back on our screens hosting a segment about the top toys for Christmas, and viewers were delighted to see them reunited with Phil, who had hosted the show.
Holly Willoughby said: "They were two of Phillip's colleagues back on Going Live! and today Trevor and Simon are back.
"But you're all finding this very weird right?"
The men all agreed with Phil saying it was "really weird" while Simon joked "For me this is like a dream come true."
Phil then told viewers they had worked on Going Live! in a neighbouring studio at the BBC's Broadcasting House.
He added: "That was Studio 7 which I think is now a hotel but here we are in Studio 3, here we are together, we have to swing our pants.
Within seconds, the three men – and Holly – recreated their iconic Swing Your Pants dance and song.
Taking to Twitter, viewers couldn't hide their delight at seeing Trevor and Simon.
One wrote: "#ThisMorning good to see Trev and Simon on the show. #swingyourpants."
Another added: "Love Trevor and Simon on #ThisMorning they need to be on tv more" while a third tweeted: "Omg relived my youth right there #swingyourpants #thismorning @TrevandSimon."
A fourth agreed, writing: "Trev and Simon!! Swing your pants. Ahh Saturday mornings were good then #thismorning."
Trevor and Simon then moved on to explaining all about the toys on display to Holly and Phil, with hilarious results at times.
Their banter sent viewers on a trip down memory lane, with one writing on Twitter: "Trevor and Simon are on This Morning and I am soooooo happy #ThisMorning #swingyourpants."
Another added: "#ThisMorning omg Trevor and Simon, swinging their pants, love it @Schofe just brilliant."
A third tweeted: "Can you book Trevor and Simon every week please #thismorning ?"
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