Sunburst

Sunburst is a male Unicorn pony. He first appears as a foal in a flashback in The Cutie Re-Mark - Part 2, when Starlight Glimmer shows Twilight Sparkle and Spike the reason why she does not like making friends. He will make an appearance as a full-grown stallion in the season six premiere.

Depiction in the series
In The Cutie Re-Mark - Part 2, Starlight Glimmer takes Twilight and Spike back in time to her youth. They witness young Sunburst and young Starlight playing a book-stacking game, but young Starlight's move almost makes the books topple over her. Sunburst saves her by using telekinesis to put all of the books back on the shelf. It is this moment that earns him his cutie mark. After which, Starlight loses touch with Sunburst and, because he earned his cutie mark before her, she starts believing that cutie marks tear all friendships apart.