Blackmail Iguana Bob: The Vault Dweller can discover that Bob's "iguana bits" meat is actually meat from human corpses supplied by Doc Morbid from Junktown. After discovering this, they can blackmail Bob into giving them money, or say that they are going to tell the police about it.
It seems, however, that the true nature of the "iguana" meat was not spread very far, as eighty years later (around 2242) Son of Bob's Iguana Bits prospers in the New California Republic, where his son, Mikey, owns the stand.
When trying to blackmail Bob into paying the Vault Dweller, one of the dialogue options is to say "Prime Choice Select is made of people!!!! It's made of people!!!" quite loudly. This is a reference to Charlton Heston's famous line from the movie Soylent Green.
Bob's vendor stand
Mikey Frazier's Son of Bob's vendor stand in the NCR Bazaar (Fallout 2)
↑BOBSIGN.MSG, an unused file with a "wanted" sign for Bob is the only place where Bob's last name appears.