That emote was honestly a blast from the past and a rather pleasant surprise. God I feel old now remembering when the Hare Hare Yukai was THE dance most anime fans wanted to emulate.
Even got our own prisoners doing it once. As a longtime fan it warmed my heart that this small reference was added. As I've probably mentioned the Haruhi series holds as a special place in my heart for being my gateway series into the Otaku culture. While it has sadly faded into obscurity I still love the series and its characters.
I now have the sudden urge to marathon the series and read the LN's again.