Buffy makes reference to Clark Kent in this episode. Clark Kent is the human altar ego of the Kryptonian superhero, Superman. The comparison is that Buffy likens herself to a superhero and requires a dual identity.
Buffy Summers: We haven't been properly introduced. I'm Buffy, and you're history!
Cordelia Chase: That boy is gonna need some serious oxygen after I'm through with him.
Buffy Summers: Oh, that's great! I kill 'em, you fence their stuff.
Rupert Giles: All right. I'll just jump into my time machine, go back to the 12th century and ask the vampires to postpone their ancient prophecy for a few days while you take in dinner and a show.
The Master: There will be a time of crisis, of world's hanging in the balance. And in this time shall come the Annointed, the Master's great warrior. And the Slayer will not know him, will not stop him. And he will lead her into hell. As it is written, so shall it be. Five will die, and from their ashes the Annointed shall rise. The Brethern of Aurelius shall greet him, and usher him to his immortal destiny. As it is written, so shall it be.
Rupert Giles: I had very definite plans about my future. I was going to be a fighter pilot. Or, possibly a grocer.