The Word Of Bob
Bob Kanefsky is widely (and justly) acknowledged as the master parodist in filk, and is likely to hold this status against all challengers. If you're not familiar with his work, check it out. Seriously. His parody-fu is the superior form.
The below is my tribute to the master. I can only apologize to Cat Faber for using her song to do it.

THE WORD OF BOB
tune: Cat Faber, "The Word of God"
words (c) January 28, 2007 by Batya L. Wittenberg

In bardic rings and dead dog filks we hear the people groan
Slanted rhyme and almost-quote and puns best left unknown
He plays with their creations where confusion makes it wrong
And counts the countless options in the bending of the song
Old, beloved lyrics and their remnants may be seen
Where tunes have left their echoes in the staves upon the screen
The authorship is clear, at least enough to be inferred:
Leslie wrote the music; Bob wrote the words.

There are those who sing of wars, of bloodied sword and shield
Crying out "No quarter!" as their armies take the field
But give Kanef no quarter and some change will soon be due:
"Tell me, please, what my poor song has ever done to you?"
Deep within the rhythm, where the counterpoint entwines
The tune has left its cadence in the space between the lines
We may shriek and giggle, or may glower in reproof:
Heather wrote the music; Bob wrote the spoof.

By star and ship and sun we see how verses start to blur
How so many songs he writes supplant the songs that were
The Spiral Dance, the Phoenix, Threes, No Man's Land, Camelot
These lovely, plaintive, moving words -- how shall they be forgot?
They have been replaced; no other lyrics can we sing
The tune has left its melody, but not another thing
We hear it twice; which version stays within our minds and hearts?
Julia wrote the tragedy; Bob wrote the farce.

And we who listen to the songs, or write our own at times
Or break the verse's structure down to see just how it rhymes
Or borrow tapes, or lyric sheets, have few excuses left;
The sincerest form of flattery is often outright theft.
Sing of coffee and of code, of guardsman, greed and gift
The tune was just left lying there for anyone to lift
So guard your songs from Songworms and from others of his ilk:
Kathy wrote the music; Bob wrote the filk.