The Black was always silent, though I don't know if you could rightly call it peaceful. Serenity surely wasn't, at that point anyway. The old Firefly's crew was in an uproar as they reacted in various ways to waking up with bunny-ear headbands and drawn-on whiskers. Wash remembered hearing something about an Easter tradition from Earth-That-Was, something to do with long-eared rodents that laid eggs, that was somehow supposed to remind people of Christ's tomb being empty.
Of course accusations were quickly leveled against him, until he pointed out that he'd been with Zoë all night. She could attest to that, too, as they hadn't actually fallen asleep for quite some time. Then Jayne (who, predictably, was the one doing most of the blaming and indignant bellyaching) pointed an accusatory finger at River, who was sitting off to the side giggling as everyone argued.
She stuck her tongue out at him. "A day is a solar-based mode of timekeeping, therefore not applicable in space," she said matter-of-factly. "Not me. It was the time-box that did it, and the girls inside."
Of course no one could figure out what in the 'Verse she meant, or if she meant anything at all, and things eventually settled down as the crew went their separate ways. Most of them cleaned themselves up after the prank, but Kaylee kept her bunny ears and whiskers—she thought it was cute. River didn't care one way or the other, and she didn't see what it had to do with the good Shepherd's book of faith anyway.
Mal, however, was sufficiently ruffled by the affront to his dignity that he flushed all evidence out the airlock and left even the subject behind, floating in the Black with a handful of pink fluff.