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September 6, 2018 11:03 AM EDT

When you’ve been on the air for 29 seasons like The Simpsons has, there are bound to be a few slip-ups with the narrative’s continuity, something that the creators often take in stride. A pretty significant blunder, however, was recently re-discovered by executive producer Matt Selman, who took to social media on Wednesday to reveal the sneaky mistake on the beloved show.

In episode 13 of the sixth season, Marge tells Homer that she’s pregnant with Maggie, but keen-eyed viewers like Selman will notice that a picture of baby Maggie hangs on the wall behind Marge even though technically Maggie hasn’t been born yet.

Selman’s discovery prompted a response from The Simpsons writer Al Jean.

And led to many speculations about the repercussions of the mistake.


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