Aparantly, no word rhymes with purple (google it, alot of people think so) but what about the word Turtle?
Thus, the birth of the Purple Turtle!

Lyrics:
"I am a purple Turtle
And i'm walking along.
Singing a song.
With my walkman on!

I go into my Shell
That is my little Dwell
To ring a little Bell
So others can tell
That...."

Big Thanks to Dr Zoom for the Backbeat, it works perfectly ^_^