Was it ever revealed who ordered the pizza Fry delivered for "I.C. Wiener"?
This was answered during the 4th season in episode 10 that Nibbler calls in the order and then pushes Fry into the cryo chamber.
In the fourth season it was revealed that Nibbler called in the pizza using the name 'I.C. Wiener'. It was a trap placed for Fry so that Nibbler can push him into the machine. The Nibblonians needed him to stop the Brains, but he was born too early.
As to who actually receives the pizza, in Bender's Big Score, Fry himself ends up eating the pizza and in the first Anthology of Interest, Zoidberg claimed to be 'I.C.Weiner'.
I.C. wiener or Nibbler, either way same character.