I have suddenly seen pictures of these all over the interwebs, and I had to try. I've seen a few variations and few notes about problems, and this is what I did.
First of all, I've heard people complain that the spaghetti gets mushy. I cooked mine on slightly under a rolling boil and used regular thickness spaghetti. I also broke the spaghetti strands in half before putting them in the sausage, so we didn't have crazy-long strands to deal with.
I've seen complaints that the spaghetti didn't cook fully inside the sausage. I used regular thickness spaghetti (nothing thicker) and used warm baked Italian sausages rather than chilled pre-cooked knockwurst or hot dogs. I also prepped the octopuses ahead by several hours and gave the pasta a little headstart on softening.
The delight of doing this? More independent toddler/preschooler delivery of pasta to mouth...observe: