The guy on the train who asked for their tickets is in quite a few tv shows, usually just one or a few episodes. He's also in quite a bit of Battlestar Galactica.
When Echidna said "my grandmother is your great-grandmother", I think she was referring to Gaia, the Earth, who's basically the mother, grandmother, or great-grandmother of much, if not most, of Greek mythology.
I kinda thought that monster was cute even in its monster form... More cat-like than dog-like IMO.