Justifying the replacement, Piers explained he and Susanna had been recruited to cover the US election this week, hosting each day as Biden VS Trump continues.
He said: "Don't check your TVs. It is a Friday, and we are here."
Poking fun at his attitude, Susanna remarked: "And good to be here as well!"
"That’s exactly what I was thinking when I woke up at four o’clock this morning, ‘oh great I’ve got to work on a Friday’," he quipped back.
"We’re here because the enormous US election news continues to reverberate around the world. It is still not concluded."
He added: "It is now down to just over 1000 votes between the two candidates."
Taking to Twitter, viewers speculated over Piers and Susanna's five-day week, with many taking it as an affront against the other ITV stars.
One said: "By persisting with Piers and Susanna are @itv executives saying that other #GMB presenters aren't good enough to host the #USElectionResults."
"#GMB Does Piers and Susanna having to do 5 days during a big story week an admission that the other presenters are only there to tick boxes @GMB," wrote a second.
"Why are Piers & Susannah presenting on days they don't normally do? Why are the other presenters not capable of talking about the US election? I have a feeling they will be gutted if the results are confirmed over the wkend," added a third.
Piers previously shared the ratings from his election coverage on Twitter, thrilled ITV had beaten rival network BBC.
Stoking the flams of his rivalry with BBC, Breakfast he wrote: "So, @GMB averaged 1.16m viewers & 27% audience share pts yesterday. That's UP by 20% & 58% on the 2016 US election.
"[email protected] was DOWN by 852k viewers (34%) & 8 share pts (20%) on 2016. Thanks for watching!"
Good Morning Britain airs on weekdays at 6am on ITV.