My girlfriend and I recently had an "argument" on whether or not eggs (ie. chicken) are the same thing (fundamentally) as caviar.  Help me out.

Well, this is not going to be very helpful, but it depends entirely on what you mean by "the same thing (fundamentally)".  Yes, caviar is fish-eggs, and chicken eggs are eggs, so in that sense they are the same.  But they differ from each other as much as the chicken and the fish do, so you might just as well argue about whether the chicken and the fish as "fundamentally the same thing".  From the persective of an invertebrate, they probably are :-)

And in both cases the eggs are generally unfertilised too.