The duke and king only invite men to the show.  Humans want the things that are forbidden to them.  The men think that the show is going to be promiscuous. 

Twain included the circus as a comparison to the duke and king's entertainment.  The circus showed how not smart Huck was.   Huck was worried about the people in the circus, because he did not know the performers were trained.  The circus was fun and entertaining for everyone.  The duke and king provided rip-off entertainment to men.

'Lizbeth is Jim's daughter.  He tells Huck about the time he beat her for not listening to him.  Jim did not know that 'Lizbeth was deaf at the time.  Jim was very sad while he was talking.  He missed his family a lot.  Twain wanted to show that slaves loved their families as much as a white man did.  Huck concludes that Jim loves his family very much.