Jeffrey Combs (who plays semi-regular Andorian Commander Shran in other episodes) plays the Ferengi Krem. This is the 2nd Star Trek series where Combs has played a Ferengi character. Combs also played the recurring character of FCA (Ferengi Commerce Authority) Liquidator Brunt in Star Trek: Deep Space Nine (1993).
The Ferengi never reveal their species name (at least not on camera). In fact, Ethan Phillips' character even says "Who we are is not important." This is likely to keep the continuity of canon as the Ferengi are supposedly not encountered by Starfleet until the first season of Star Trek: The Next Generation (1987).