Probably, yes. Other ponies have worn hats at various times; for example, Rainbow Dash occasionally wears athletic hats, Twilight Sparkle has a wizard hat which she uses for cosplaying, and Rarity has hundreds of fashionable hats that she wears when the occasion is right, from chic little berets to a giant hat crystal-encrusted hat that is almost as big as she is. (my favorite is probably Pinkie Pie's top hat, but that's mostly because the tuxedo she wears with it is adorable, on account of the tuxedo socks. There are not enough canonical outfits that include socks) However, the only pony who wears a hat (almost) all the time is Applejack, so she is most likely the one you are thinking of!

Well, Braeburn wears a hat all the time, too, but I don't think he is in this video.

He loves the show! He's an active brony and even does voice-overs for fan work.

His character, Discord, is one of the show's most popular villains. Discord is basically Q.

Oh! I knew I knew that voice from somewhere. According to his imdb he was also on Breaking Bad and a bunch of other things. More than anything else, MLP seems like a really fun show to be a part of, especially as a voice actor.

If you're interested in Mr de Lancie, here's one of the coolest things he did:

http://youtu.be/OV-OF9wZWDs

He sings about hipsters, Tumblr dorks, and clopping.

Little kid's shows must be fun work for a VA, given that subtlety is still an alien concept to the audience (targeted or otherwise). You get to overact as FAAAABULOUSLY as you want!

22 minutes is really stretching it for a YTP though.