Ahead of an ad-break on the morning news programme, Susanna was expected to read out the words: "You're watching Good Morning Britain on ITV."
However, when the autocue outlined the script, Susanna refused to read it out, and instead silently sipped on a cup of tea.
Piers was baffled, as he scoffed: "It's her turn to say it."
Susanna quickly swiped back: "Your go."
The camera showed the two presenters holding up their GMB mugs of tea, both stubbornly refusing to speak.
Piers then alleged: "It's beneath her to do the 'You're watching Good Morning Britain on ITV'."
Susanna objected to his claims, but then allowed Piers to read out the offending line – even though he did so begrudgingly.
Laughing, he read out, "you're watching Good Morning Britain on ITV," and the credits began to roll.
Luckily, there were no hard feelings between the presenting duo, because once the break ended, they were preoccupied by a conversation about tea.
Piers was inspired by Susanna's tea-sipping to count the number of brews they were downing each episode.
Reaching out to one of the runners behind-the-scenes, Piers was horrified to learn he chugged a whopping seven cups of tea while filming GMB.
However, Susanna trumped him by a long shot, knocking back an impressive 10 cups of tea and coffee when the cameras were rolling.
Their co-star Lorraine Kelly couldn't believe the number, and confessed she'd be constantly nipping to the loo if she drank that much tea.
Susanna quipped in response: "I feel like we’ve had too much information on this particular item!"
Good Morning Britain airs on weekdays at 6am on ITV.