Here had we now our country's honour roof'd,
Were the grac'd person of our Banquo present;
Who may I rather challenge for unkindness
Than pity for mischance!" (Act III Scene IV) * Banquo should be there as a guest, he was one of Macbeth's closest friends. Macbeth pretends to wish that Banquo was at the celebration, his false sense of sadness at the absence of his friend may be the cause for the ghost's arrival in the room shortly thereafter.
Prithee, see there! behold! look! lo! how say you?
Why, what care I? If thou canst nod, speak too.
If charnel-houses and our graves must send
Those that we bury back, our monuments
Shall be the maws of kites." (Act III. Scene IV) * Macbeth first sees the ghost sitting in a chair and is shocked and frightened by the sight. He can't believe his eyes, but no one else can see the ghost.
I pray you, speak not; he grows worse and worse;
Question enrages him. At once, good-night:
Stand not upon the order of your going,
But go at once." (Act III, Scene IV) * At this point, Lady Macbeth gets very nervous about what her husband is saying in front of his court and she tells everyone to go home that the King is just not feeling well. He is having a kind of fit that will pass.
3.) Banquo's ghost represents Macbeth's guilt towards killing his friend. Macbeth's conscience is appearing through Macbeth's tough and ruthless exterior and shows that the former (less ambitious) Macbeth did not die completely.