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.
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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?"