I created the Carl Sagan Is My Homeboy shirt as a parody of the Jesus Is My Homeboy shirts as a kind of reasoned protest. I found only later that there was already a similar shirt featured on the Weird Al video "White and Nerdy". Still to this day, yellow has been the most popular color of this design on my site. So to Weird Al, as well as to the original Sagan is my Homeboy creator, you are awesome.
So, without further adieu, I present to you both the white and nerdy version as well as my own.
Weird Al's White and Nerdy Carl Sagan Is My Homeboy shirt