The surprise performance from the Star is Born co-stars has produced a huge reaction from fans, with many excited to see the pair reprising one of the film's most popular moments.
But for all those fans getting excited about the duet itself, there were also plenty of people left fascinated by the duo's chemistry on stage, with many theorising - and this is the key word here -that perhaps there might be a little more to their relationship away from the public eye.
One Twitter user posted: "Wish these 2 were a real love story the way they look at each other."
Another said: "I ship them together. They have amazing chemistry."
Lady Gaga and Bradley Cooper in A Star is Born - which of course is fiction, not real life. Credit: Warner Bros
But this being the Internet, not everyone was quite so subtle, with one person simply posting: "Bradley must be knocking off lady Gaga, the dawg."
'Must be'. That's a confident statement there, pal.
Meanwhile another person coyly posted: "I wonder why he was in Vegas?"
Well, quite. Work? Leisure? Simply to perform a duet? We can only speculate.
Others were happy to just quote a popular meme and leave it at that, with several people posting: "Find someone who looks at you the way Bradley Cooper looks at Lady Gaga."
Still, wild conjecture aside, people really did love seeing them on stage together.
Of course, as much fun as this has clearly provided for fans with social media, fertile imaginations and too much time on their hands, it is just speculation - the pair are both in long-term relationships with their respective partners.
Cooper has been in a relationship with Irina Shayk since 2015 - the pair have a child together - while Lady Gaga (real name Stefani Joanne Angelina Germanotta) has been with Christian Carino since 2017.
Sorry to disappoint you, fans of scurrilous gossip, but it looks like that's all there is to this one.
Cooper's take on A Star is Born is the third remake of the original 1937 flick, having been previously adapted for a 1954 musical starring Judy Garland and James Mason, and a 1976 rock musical with Barbra Streisand and Kris Kristofferson.
Gaga's performance in the film has even nabbed her two Oscar nominations, for Best Actress and Best Original Song.
Speaking to LADbible last year, Cooper said: "It was one of the great experiences artistically I've ever had, and oddly natural. I had the privilege of working with so many great artists in this film."
Featured Image Credit: PA