Knockout was your sparkmate for... A few months now. You had asked him out and he obviously said yes, because he actually felt the same way.

You were in the medbay helping him with his work, ever since Starscream was the new commander after Megatron was in his half way dying, you have been helping him. Today, you were in the medbay all alone, since he went out racing among the humans, like usual.

a few hours later, you could hear him walk in the medbay.

"Doctor in the house."