The great Overdog
That heavenly beast
With a star in one eye
Gives a leap in the east.
He dances upright
All the way to the west
And never once drops
On his forefeet to rest.
I'm a poor underdog,
But to-night I will bark
With the great Overdog
That romps through the dark.
The speaker has been contemplating his position in the universe and now wants to rise to the same level as the great Overdog. 
 Alternatively, the speaker has been inspired to join the Overdog in truly living his life, without inhibitions. 

Canis Major