Ah, a Pandroan... Which TAS episodes have they not referenced yet?
Timo Saloniemi
Going through the list, they have referenced (in some oblique manner):
* Yesteryear (Aurelians)
* More Tribbles, More Troubles (grain ship)
* The Survivor (Vendorians)
* The Infinite Vulcan (Giant Spock, Phylosians)
* The Slaver Weapon (Kzinti Telepath)
* The Jihad (Nasat)
* Bem (Pandroans)
You could argue for Beyond the Farthest Star as the first appearance of an Edosian (Arex).
That's seven or eight episodes referenced out of 22 (~35%). In contrast, franchise-wise, they have referenced seven of nine series (heh)* or ~78% of the franchise as a whole.
*TOS (Mitchell, et al), TAS (see above), TNG (Crusher, et al), DS9 (shown), "VOY" (Paris, et al), Enterprise (Riker's holoprogram), STPicard (Daystrom Institute). No refs to Discovery or Short Treks, I believe.