But "The fun has been TRIPLED!" wouldn't be accurate since season 3 only has 13 episodes, half of what seasons 1 and 2 had. Therefore the quote would have to be something like "The fun has been multiplied by 2.5!" instead. That is, of course, if we assume that season 3's episodes contain exactly the same amount of fun as episodes from the first two season. Obviously this might not be the case; season 3 might even contain DOUBLE the fun compared to previous seasons, meaning that "The fun has been TRIPLED!" might end up being accurate after all.
I'm rambling, aren't I?
The inaccuracy of it occurred to me as soon as I wrote it, which was why I came up with "Half the episodes, same great taste", but I'm not really liking that one. It's a play on old diet food-and-drink TV commercials, but that has nothing to do with Ponies. And I don't think we can judge Season 3 before it airs (aside from assuming it'll generally stick to the course it set), so some inaccuracy doesn't matter.
"The fun has been TRIPLED!" is just a previous-season quote adapted to have some simple "season 3" meaning. And it implies that we're going to have fun. Three times as much fun.
"We didn't learn anything!" is a previous season quote that doesn't adapt to any specific season or thread, but it suggests that we're suckers for Pony. It's good. It would be best used following some sort of Pony War that should've turned us away but didn't, but we don't seem to have any of those handy. And I think it might be a bit too much self-deprecating humor after the current Derpy quote. Gotta space these feelings out and have variety.
"By now, it can be considered a lifestyle" seems a touch too "brony" to me, and for a return to the OT, I wouldn't want to scare anyone away by acting too creepy.
I really like Fluttershy's understated "Yay!" and the old "Time for Ponies" meme, but Luna's triple happiness is just working best for me right now. Still room for more brainstorming though.
Okay, so maybe my idea sucks...
Bad ideas are a perfectly normal part of brainstorming.