The headline on one of the newspapers outside Bosco's inconvenience reads: "Purcell attacked by two headed monkey". Steve Purcell is the original creator of Sam & Max and two headed monkey refers to a line in the Monkey Island games. When Guybrush Threepwood wants to escape from a tricky situation, one of the lines you can often use is "Look behind you, a three-headed monkey!"
Sam can ask Bosco for random items. One of the things he mentions is a snow globe of the Mystery Vortex. This is one of the items from original game.
When Sam & Max first arrive at the White House, Sam says "Here we are, standing in an open field west of the White House." This is a reference to the opening sequence of Zork: You are standing in an open field west of a white house, with a boarded front door.