I think this is what a lot of progressing couples get wrong. The 'teasing the one you like' thing? You may have seen your parents do it, sure, but that's because they're already married and have more free reign to do that kind of thing. You try doing it on your crush who's unaware of your feelings, and they'll probably take it as bullying and wonder why they're being bullied.
It somehow worked out for these two, but now that they're official, the 'teasing gauntlets' are sure to be thrown down.