As with the original "Die Hard" it is referencing, when Ozzie navigates through the building by climbing through the air ventilation system, it is like when James Bond did it in this movie.
When the sprinklers are going off Ollie turns off the water main and refers to Melvin as "Number One". (Pointing to what Patrick Stewart, as Capt. Picard, called Cmdr. Riker on ST:TNG.