The 50-year-old presenter was shooting a segment for the ITV breakfast show's £100k give away phone-in competition on a boat at the Rickmansworth Aquadrome when he mentioned a viewer had contacted the show to say they had seen a strange creature lurking on the banks behind him.
Peters and hosts Adil Ray and Ranvir Singh in the studio laughed off the supposed sighting.
Viewer and video journalist Matt Capon posted a clip on Twitter, captioned: "When I heard @andipeters mention that #GMB viewers had spotted something on the banks of the lake in Rickmansworth I went back and had a look..."
But GMB producers have since played back the footage - which shows a black animal with a tail, the size of a dog, emerge the bushes in the background and walk along the bank in the prowling manner of a feline.
Series director Erron Gordon tweeted: "So myself and two of our fab @GMB team @CameronDLWalker & @xemilymulliganx had a look at this post show in the newsroom and I’m certain it’s a dog, Emily and Cameron think otherwise #ItsADog."
GMB team member Emily Mulligan posted: "It's a wolf."
Sen Monro replied: "If that's a dog cuzzie, then I'm staying this side of Hertfordshire!! That looks like very large wild cat."
While some eagle-eyed viewers and Twitter users are speculating it is a big cat, others think it could have been a wolf.
Liz Little claimed: "Black panther made it's way to the UK!"
Kath Wilson tweeted: "It did catch my eye.. looked bigger than a dog at 1st glance but could've been the angle.."
Watch: Big cat sighted in Welsh hills in February 2021