Learn by doing, right?
Reading through the FATE rules, I made a simple character as I went along. Perhaps you remember Robot Unicorn Attack hitting it big a few years back? I figured that's about as straightforward as videogame characters get, so here's what I came up with:
As far as I can tell, the Robot Unicorn has no name. I just picked "Rob" as a handy abbreviation.
The character's High Concept is totally already defined. Robot Unicorn: exactly what it says on the tin.
The Trouble aspect was trickier. At first I was leaning against having Priceless Horn as the aspect, because Trouble aspects are not supposed to be redundant with the High Concept. The book gives the example that a character with the high concept Lead Detective shouldn't pick the trouble aspect Hated By The Underworld, because that drawback is already implied by the high concept. But I thought about it, and attempted horn thievery is not as universal a plot complication as I'd initially assumed. Sure, Darkness wants unicorn horns, but the villains of The Last Unicorn want unicorns themselves, not the horns, and I don't remember Unico having to avoid horn-poachers either. That said, perhaps the aspect could be made more specific, like "Horn Coveted by the Cyberwizards" or "Horn Valued as Droid Aphrodisiac", but this will do for now.
The Genre aspect (remember, I'm not using the games default "phase trio" for the last three aspects) was surprisingly easy. Rather than try to define the genre of the setting (synthpop fairytale robo-fantasy?) I just picked the gameplay genre. Endless Runner can totally be invoked to justify bonus relating to movement or stamina or whatever.
The Catchphrase aspect seemed tricky at first, since Robot Unicorn doesn't talk at all. But even though there's no dialog in the game, there is a catchy and iconic theme song. So I took the most memorable line from that, which presumably reflects the character's intense loyalty, or something.
The Wild Card aspect was actually challenging to come up with. After going through the wikipedia page for Robot Unicorn Attack a few times, I settled on Pixie Collector after the game's bonus point mechanism. I'm not exactly sure what this entails, but one of the neat things about FATE is that the aspects invented to describe the characters can also contain details to help guide the GM's worldbuilding. And since at least one Disney film setting does include pixies, this character would motivate me to make sure those pixies show up in the campaign, ideally sooner rather than later...