怪物くん or Kaibutsu-kun and his companions, ドラキュラ = Dracula, オオカミ男, Ookami-Otoko = Wolfman, and フランケン = Franken, travel from Kaibutsu Land to the Human Realm, where they encounter and battle several monsters, mainly assassins from the demon group Demonish. There were two Anime series, 1968-8 and 1980-2 and I have seen neither one.
I managed to UFO catch these guys a few years back but had no idea from where they came (never saw the Wolfman or I would have snapped it up as well.) A colleague recognized them and pointed me in the right direction and now I shall point you in that same direction...
I'm going to keep an eye out for more of this series. It's pretty messed up!