As the sisters were arguing, one viewer became distracted by a man in a high-visibility jacket stood watching in on the scene.
As nasty Babe told a distraught Sylvie she is "nothing", the man was seen beside Syvie's left shoulder.
The fan tweeted: "@bbceastenders so now your staff are in episodes?? #EastEnders."
Last night's episode saw Aunt Babe sensationally leave the show after cursing the Queen Vic.
It seems that Aunt Babe and Sylvie were not alone during their row
An eagle-eyed viewer noticed the mysterious man
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Babe's uncomfortable scenes with dementia-suffering Sylvie left many viewers disturbed by the former's actions.
This is not the first time that viewers were quick to point out oddities in an episode.
Most recently, fans noticed a hand holding a rat's tail inside the Minute Mart before it scurried off.
Aunt Babe sensationally left the show last night after distressing scenes with Slyvie
Another gaffe showed a hand holding a rat's tail in place
Fans were quick to air their amusement on Twitter, with one writing: "Great work by #EastEnders hand and rat!"
Another asked: "#EastEnders Anyone else see the hand on the floor grabbing the rat outside the shop?"