Mediocre to good tv shows that have beyond good episodes?

[the-pi-guy]

The thread premise is basically:

Are there any mediocre TV shows that have a particularly good/great episode?

Or any good shows that have all time great episodes?

[Legend]

The pilot episode for lost was pretty great.

South Park's Tolkien episode was great.

In general though it's hard for me to think of tv shows on a per episode basis. Seasons sure, but not episodes.