Although Shankman's Rubbing Compound is not a real product, Charleston Chew is.
On Embassy Row, Zoidberg runs past the Neutral Planet embassy, the Klingon Embassy, and the Globetrotter Homeworld Embassy.
When Zoidberg recounts the story of his childhood on Decapod 10, he mentions his mother. Because decapodian die after mating, it is likely that Zoidberg, and all others of his species, are reared by an adopted family rather than his biological one.
When Bender first plows through a crowd as the "Freedom Train", the third person who jumps out of the way is Michelle, Fry's 20th century girlfriend.
In the Museum of Ancient Weaponry, there is a gun titled "Dillinger's Semi-Automatic Salad Shooter". This is a reference to John Dillinger, an infamous bank robber during the 1930s.
Zoidberg was clearly given an unfair trial as he was sentenced to death by the supreme court. According to the Constitution, the supreme court cannot sentence anyone to death because their rulings against defendants do not count as convictions. They also can only do lawsuit trials that concern laws that violate the constitution and they cannot do any criminal trials. This was presumably changed in Into The Wild Green Yonder when the Ecofeministas were given a criminal trial by the Earth Supreme Court. This change signals that Zoidberg was given the right to appeal by law but it was violated. It may be that Zoidberg used his right to appeal and won his appeal trial.