The note in alien code which Leela receives translates to "Need extra cash? Melt down your old, unwanted humans. We pay top dollar!"
The old man asking for his death certificate, was in line to get his birth certificate in How Hermes Requisitioned His Groove Back (2000)
The number on the door of the Cubicle Room in Central Bureaucracy is 729 - nine cubed, which is the number of cubicles in the room.
While walking through Tijuana, Bender and Hermes pass a photograph developing business in an adobe building, appropriately called the "Adobe Photo Shop," a literal take on the famous photo editing software.
The Professor calls Bender a "mortal coil". This is a reference to Hamlet's famous monologue in Act 3, Scene 2. The monologue begins "To be or not to be".