Definitely evident, and Megatron is hard pressed not to laugh again, smothering it by swallowing instead. It pleased him, that surprise as well as the, ahem, obvious reaction even if he should perhaps hold Optimus' hips down to avoid getting things slammed into his faceplates more than necessary.

Still, the smug smile, even stretched out around Optimus' spike as it was, was probably as obvious as Optimus' surprise which Megatron was taking his own pleasure in catching glimpses of.

His thumbs stroking along short stretches of seam that they'd found, Megatron drew upwards again, teeth locked enough around the spike to scrape along it, but not much more. The charge snapped from the more sturdy material of his teeth to the softer and thinner metal elsewhere in his mouth, and sensors sent out warnings of sensory overload and too much charge, possibility of impending damage and then left behind prickling and then ozone-tasting emptiness as the sensors shut down and left things numb.

He didn't really mind. He'd done similar things before, even if there was a reason it was more clever (and more comfortable) to stimulate a spike into charge rather than after it'd already gained a charge.