I don't watch Babylon 5, but apparently it is. He's fairly recognisable.
Most of the actors are Irish ones, so obscure outwith the show. Otherwise, Vernon Dobtcheff is the casino owner who Jaws kills in The Spy Who Loved Me, the Scientist in the Doctor Who story The War Games, and thousands of other roles. Richard Wilson is Victor Meldrew. Gerard Murphy was in Silver Nemesis and Denys Hawthorne in Terror of the Vervoids (both Dr Who). Peter Caffrey was in Ballykissangel, Clare Grogan is a former pop star (Altered Images) who was in Gregory's Girl, and Graham Norton and Tommy Tiernan are now internationally renowned comics...somehow.
Oh, and Declan Mulhullond was a drunk who once played Jabba the Hutt in Star Wars.
Father Ted is great, one of the finest sitcoms ever made. And entirely accurate too.