And they've now got together again in a video that appears to hint that Sheeran has new music on the way.
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The clip posted on Instagram shows the duo sitting alongside each other at the piano, with Cox tinkling the ivories and Sheeran strumming a guitar.
The star then sings a couple of notes, before the pair stop and smile at each other.
The caption was simply "25th June", which has fans thinking that Sheeran is unveiling new music that day.
Some think Sheeran was actually hinting that he and Cox have another collaboration in the pipeline.
"25TH JUNE WHAAAATTT?!?!?!?! A COLLAB !?" one fan posted.
"What is happening???" asked another, while one excited follower said they were "so here for that".
"A Monica and Teddy Collab is what we wanttttt!!" said another.
Fans of both Cox and Sheeran were already in a meltdown last week when the pair recreated The Routine, not long after Friends: The Reunion aired.
The dance was first performed by Cox (Monica) and David Schwimmer (Ross) in the 1999 Friends episode The One With The Routine.
In a video posted to Instagram and captioned: "Just some routine dancing with a friend…", Cox showed she still remembered every move.
Sheeran kept up perfectly until the lift at the end, when he and Cox collapsed in a heap on the ground.
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