Welcome to Gaia! ::

Nikki- Tim Kring, the creator of the show, stated that he originally created Niki with the power to be in two places at once, which stems from her life as a single mother. Niki was also originally written to be a showgirl. However, Ali Larter did not have the proper physique to portray a showgirl, so the character's profession was changed to internet stripper.

Sylar- The original concept of Sylar was of a killer who ate his victims' brains and "digested their power"; however, in order to avoid the potential silliness and zombie associations, the producers deliberately made this fact vague in the series.

Hiro- was one of the last main characters to be created by Tim Kring; he was added to the pilot episode after Kring's wife noticed none of the existing main characters were happy about their powers. Hiro was named so his family wouldn't forget Hiroshima.

Peter/Nathan/Parkman-La Padura states the Petrelli brothers were originally written to be twins, and it became obvious in the production process that in order to have correct dynamic between the two characters, Peter had to be the younger brother. Milo Ventimiglia's role as Peter was one of the last to be cast and the most difficult. Greg Grunberg originally auditioned for the role of one of the Petrelli brothers. It was not a fit for him, but the production liked him so much, they rewrote the role of Matt Parkman to fit him. Originally Parkman's character was to be much younger, and La Padura was looking to cast a Ryan Phillippe-type actor for the role.

Mohinder-The role of Mohinder was originally written to be a 55-year old geneticist looking for superpowered humans. However, Sendhil Ramamurthy's audition was so convincing that the main character part was rewritten to be a younger geneticist following in his father's footsteps.[2] The concept of the older geneticist was spun off into the minor character of Chandra Suresh. Most Heroes episodes begin and/or end with a voiceover by Mohinder.

very interesting... I only knew about the Petrelli bros