There are "hidden" NPCs all around Gridania during the Hatching-tide event. Here are the ones corresponding with Patch 6.1. (I may miss some of them; if so, please leave a comment and I'll add them to this list.)
**Added missing (Raven-furred Rabbit). Thank you, Celis Antares!
Pink-furred Rabbit (Tataru Taru) - Old Gridania, Shaded Bower (14.5 , 9.3)
Pink-furred Rabbit: Oh, Mai! Here to enjoy the festivities, are you?
Pink-furred Rabbit: Not me, of course! Why, I'm here on very important business─conducting market research to bring further fortune and profit to the boutique!
Pink-furred Rabbit: But I must say, this suit is simply the perfect combination of comfort and style. Perhaps I should have them mass-produced and add them to my lineup of wares...?
Thrillingway & Well-oiled Rabbit (Godbert) - Old Gridania, under the Leatherworkers' Guild (12.0 , 8.6)
Thrillingway: Mwahaha...! The day is mine! To think I would find fellow goo enthusiasts here on Etheirys!
Thrillingway: I do wonder what manner of mousse slime they're using. Yes, I simply must ask! Once all these people go away, at least...
Well-oiled Rabbit: Oho! Gridania's artisans have clearly outdone themselves with this year's decorations! I can feel the inspiration swelling up from the depths of my very soul!
Snooty Rooster (Emmanellian) & Rooster Retainer (Honoroit) - Old Gridania, The Whistling Miller (8.9 , 7.8)
Snooty Rooster: <WoL>, old girl! Always a pleasure to see you! Enjoying the festivities, I take it?
Snooty Rooster: What's that? You don't recognize me? You wound me, my friend! And after all we've been through together!
Snooty Rooster: I must say... I had thought Gridanians to be all dour-faced gardeners and carpenters...but this festival could put even the masquerades back home to shame! If only my dearest Laniaitte could be here to enjoy it with me...
Rooster Retainer: My Lord... I realize that you are undercover, but nevertheless─I must ask that you comport yourself in a manner befitting your lofty station.
Fatherly Rooster (Gaius) & Daughterly Hen (Allie) - Old Gridania, The Whistling Miller (west) (8.5 , 8.7)
Fatherly Rooster: Just my luck. Dragged off to this frivolous festival, and now I encounter you of all people.
Fatherly Rooster: And yet...a father cannot very well refuse his daughter's earnest plea.
Fatherly Rooster: Needless to say, you will say not a word of this to Severa or Valdeaulin. I would never hear the end of it...
Daughterly Hen: Is it truly you!? Oh, I can hardly believe my fortune! It wasn't easy to convince Father to bring me here, but it was worth every little white lie and good deed!
Daughterly Hen: Of course, we're not here simply for pleasure─we have an important missive from Werlyt to deliver to the Adders' Nest. But there's nothing wrong if we enjoy the season while we're here, yes?
Daughterly Hen: More than anything, I want to share with everyone what a vast world of joy and merriment is out there! After all, what did we risk our lives for if not this?
Azure-furred Rabbit (Seiryuu?) - New Gridania, Blue Badger Gate (14.0 , 14.3)
Azure-furred Rabbit: Finally...you have come. How long has it been since we met outside the temple?
Azure-furred Rabbit: If you are wondering why I would make this journey so far to the West, it is simple─I had a vision that a little red sparrow and a mewling white kitten went off to visit you without me.
Azure-furred Rabbit: Dream or reality, I swore that I would not suffer such ignominy. And so I have come to claim you for myself. Yes, soon we shall settle the score of who is most worthy to stand at your side...
Resplendebt Rabbit (Byakko) - New Gridania, White Wolf Gate (9.0 , 13.0)
Resplendent Rabbit: We meet again...and to think it would be in a place like this. I must say, the customs of your land are most fascinating.
Resplendent Rabbit: Were Tenzen here, no doubt he would have mistaken those two-legged rabbits for auspices, and attempted to recruit them into our ranks.
Resplendent Rabbit: Speaking of which, have you met the others yet? If not, 'twould be best if you hurried along in search of them. Were they to find out that I had kept you all to myself, I fear for how their aramitama might respond...
Vermillion-furred Rabbit (Suzaku) - New Gridania, outside the Carline Canopy (12.1 , 13.6)
Vermilion-furred Rabbit: I am most pleased─if not surprised─to find you here. After all, Tenzen, too, quite enjoyed festivals...and the two of you are alike in so many other ways.
Vermilion-furred Rabbit: I had meant to come alone, but my fellow auspices insisted on coming along for the ride─and quite literally, at that. Just look how my plumage has been ruffled by their clinging paws...
Vermilion-furred Rabbit: And yet, were Tenzen here, no doubt he would have gently reminded me─“the more, the merrier.” With only the slightest hint of disappointment on his face...
**Raven-furred Rabbit (Soroban) - Old Gridania, Lancer's Guild
Raven-furred Rabbit: Well, if it is not <WoL>! Genbu had hinted to me that our paths would cross again, but I did not expect it would be so soon. Yes, ever since we became one, I have been having more and more of these...premonitions. Most of them are less than auspicious, so let it suffice to say that this one was most welcome. And yet, intriguingly, this is not the future I foresaw. And so I must conclude that we are destined to meet again. Under what circumstances, I know not for sure─but I look forward to that day.
There is also a Raven-furred Rabbit(Soroban & Genbu? ) near the Lancer's guild.( X:13.2 Y: 5.4 )