The customer, from Singapore, claimed he bit into a Sausage McMuffin and found a baby lizard, reports The Consumerist.
The customer originally posted the photo on the McDonald's Singapore Facebook page.
The sandwich was promptly sent to a lab for testing.
McDonald's said in a statement on Facebook that the mysterious apparition was actually a chicken vein.
"The sample collected is 100% chicken," McDonald's wrote. "The vein is white in colour because of the Halal slaughtering process where blood had to be drained."
Here's the original photo: