One day, Spike is rummaging through some old stuff in the library when he comes across a picture of a young Twilight and another dragon named Derek. When he asks her who he is, she explains that he was her assistant and best friend years before Spike was born.

So Spike decides to set off to find Derek and return him to Twilight. Eventually, Spike does manage to find him and bring him back, which makes Twilight overjoyed.

After Twilight introduces Derek to her friends and all of Ponyville, Derek goes to live with Applejack and begins to develop an accent just like her, as well as countryisms (even though everypony insists it is fake).