"Spike..." Rarity breathed quietly, almost a whisper. Spike didn't respond, too lost in the euphoria of this dream made reality. He felt that if he spoke, if he did anything, the little world about them would burst like a soap bubble. She spoke again, even softer this time.
"You have something in your teeth."
"Oh come ON!" came the anguished cry from behind the sofa.
yes, she is, until she realized how close her face was to Spike’s. Her nose was almost pressed against his, she could actually feel his warm breath over her snout. Without thinking, her eyes fixed themselves on his, which were staring right back at her. Both their hearts were now beating at a hundred miles per hour, it felt as if they were going to explode at any moment now. The unicorn didn’t even notice she was leaning closer, her lips ever so closer to his. Her mind went blank as she got closer and closer to her dragon. Spike thought he was dreaming as she started leaning towards him. Was she going to kiss him? It certainly looked like it, but it couldn’t be so soon! Oh, what the hey! The dragon closed his eyes and he too leaned forward, contributing to making the ever diminishing distance between their lips smaller...
He can't be with her! Twilight wouldn't just let Spike have a serious relationship like this! He is far too young! Much too immature and inexperienced. For something so new to Spike, he should be with somepony who understands romance, Somepony that knows how special love is.
Not to mention both are far too busy to even consider this! Do you think that Spike would take even a moment to falter on his prestigious position with assisting Twilight to resort to helping a dressmaker? It would take serious dedication to resort to such a rash decision!
And she can't be with him! Spike is practically a prince with Twilight being a princess now. Imagine the scandal! Royalty mingling with the common pony? It's unheard of! It's preposterous! A fairy tale even! Only a pony with a flair for the fanciful would concieve such an idea.
What of Rarity's career? Spike does well as an aide but he is certainly no pony! Do you expect Rarity to just open up a line of draconic fashion? Ha! The fabric costs alone would be outrageous.
Lastly, Did I mention Spike is not a pony? A dragon and a pony!?!? It's forbidden! Prohibited! Taboo! Illicit! Where does it say a Pony and a Dragon can be together?!