Ernie and Arnie are Alf's friends / assistants / test subjects. They're a couple of mischievous ants who cause all kinds of problems for Alf. Don't ask me which one is Ernie and which one is Arnie. I forget.
Creator Commentary: So what's in a name? I have repeatedly had people hassle about Alf's name. Yes, I realize Alf (Alien Life Form) was a popular sitcom in the 80s. But Alf was an ALIEN (technically an alien-shaped puppet). My Alf is an ANTEATER. WHO INVENTS CRAP. There's NO correlation between those two characters at all. Plus, I'm pretty sure you can't copyright a proper name. However, if I am ever sued over the name, I have a backup name: Alfred.