I’ve made a little compilation of all the notable Whouffle and Whouffaldi moments over the seasons, along with my thoughts and theories:
Their relationship was set up as romance right from the very beginning with these words, because it becomes obvious right away that Clara might be romantically interested in the Doctor by hinting at future snogging. I don’t believe that she immediately jumped him, but she let him know from the beginning that she wasn’t uninterested.
Let’s jump to “The Crimson Horror” where Eleven and Clara pose as husband and wife and they both convinced Mrs Gilliflower, a woman who is anything but stupid. In fact, they both seem to enjoy it, too.
I always like to believe that the end of “Nightmare in Silver” is the moment Eleven realizes that he fancies Clara because he notices her on a physical level. Besides, the conversation Mr Clever had with Clara in which “the Doctor” confesses his love to Clara is probably based on the Doctor’s own thoughts to which Mr Clever had access at that moment, but Clara saw through it and knew that the Doctor would never admit it.
When Clara suggests that she needs a boyfriend for Christmas dinner Eleven was excited. He actually believed that she was serious for a moment and he was more than happy to be her boyfriend, yet at the same time he was a bit worried that he might disappoint Clara. It was Eleven who was disappointed when he realized that Clara wasn’t actually serious.
Unfortunately they never really got to explore that part of their relationship because he got stranded on Trenzalore and later regenerated.
Matt Smith has confirmed that Clara was sort of his girlfriend while Jenna said in an interview or during a panel that Clara realized she was in love with him during the regeneration.
I May or May Not be Steve Rogers 