One example might be in the very first chapter when Twain writes about prayer. He describes Miss Watson and the widow trying to teach Huck how and why one should pray, and Huck takes what they say very literally. They say that if you really want something, you can just pray and pray for it. Huck's commentary on this is that he tried it, and it didn't work (he prayed to find a fishing hook). Twain clarifies, through Miss Watson and the widow, that what you pray for is not fishing hooks, but to be a better person, and other such spiritual "gifts"; Huck immediately rejects this, because who wants those kinds of things anyway, and decides that prayer is useless. Twain could be cynically commenting on the seeming "unfairness" of prayer, and on the illogical nature of asking for things that, on the surface, don't benefit us much. He is using Huck to present a more "logical" view of something, a more practical approach to it. And, even though Huck describes his reactions very seriously, the end result that Twain produces is very humorous and entertaining.