Marathon has several levels named after quotes from Beavis And Butthead, such as the first level with lava being called "FIRE! FIRE! FIRE! FIRE! FIRE!," or the level with the first hidden flamethrower called "Smells like Napalm, tastes like Chicken!"
Marathon level names are loaded with shout-outs... and bad Pfhor puns. Sometimes both at once.
In "Rise Robot Rise", Tycho says, "Don't sweat the details, little monkey. Leave the strategizing to those of us with planet-sized brains", a clear reference to The Hitchhikers Guide To The Galaxy, in which Marvin complained, "Here I am, brain the size of a planet, and they ask me to take you to the bridge. Call that job satisfaction? 'Cos I don't".