It wasn't Mike and Angelo...

That was on ITV, and featured some annoying Yankling in big white 80's trainers. This was on the Beeb, and was just as bad, but had no embarrassing grabs at transatlantic popularity. Teenage lad makes friends with an alien who wore nasty shellsuits and who (either because it was a cheap way to make him look alien or because his race were shapeshifters and got bits wrong, like Odo on DS9) had back-to-front ears. He also had this weird amulet thing and if he lost it, he'd gradualy start to weaken and fade away, which of course happened every episode.

Any ideas?