Notes:

Explanations on the winning squares:

Diagonal:

"Large role for a background pony" – Bulk Biceps wins this one. He went from a one-note gag to a character with a name, a spot on the Equestria Games team, and adorable shipping fuel with Fluttershy.

"Flying lessons" – we got that in "Princess Twilight Sparkle," the season opener.

"Free hugs" – duh.

"Season 5" – also duh.

"Separation anxiety" – this one is a bit vague, but there are a few instances that might count. the big one, though, is Seabreeze being worried about not going to see his family in "It's Not Easy Being Breezies." If being worried that you'll never see you kid again doesn't count at "separation anxiety," I don't know what does.

Vertical:

"New sapient species" – the breezies.

"Scootacripple" – in "Flight to the Finish," the fact that Scootaloo should be able to fly by now is a major plot point.

"Luna Episode" – the plot of "For Whom the Sweetie Belle Tolls" is mostly driven by Luna, so I'm counting it.

"Season five" – duh, again.

"New family member shows up" – Maude Pie.