Ratchet was never fond of humans. He didn't find a use for them. They were loud, annoying, got under-pede, and they never stopped asking why. It didn't matter what you told the little brats. They would want another explaination to the one you just gave them.
He sighed and tapped several keys a little too hard. It got Optimus' attention. The Prime raised on optic ridge as he let Jack climb onto his shoulder. The human had been trying to show him something or another. Ratchet hadn't cared what. He had just wanted the humans gone. They had been fine before this.
That was before he met an adult human. The time when Ratchet hated humans was known fondly as BJ.