Roger & Steve: (Fly over a billboard of a full moon on bike)
The scene where Roger & Steve fly off the cliff on the bike with the picture of a full moon on the billboard behind them, is a reference to the famous scene from the movie, E.T. The Extra-Terrestrial. It is even more obvious as Roger is wearing the sweatshirt with the hood on while riding on the front basket of the bike.
The billboard itself is also a reference, to Jay and Silent Bob Strike Back, who mocked E.T. in their movie through the use of a billboard background in Hollywood.