Pippin in the book?

[Evisse the Blue]

Pippin is surely the most childish of all the hobbits, but that does not always prove a bad thing, for himself or others. For instance, anyone less happy go lucky and lighthearted would have broken down during those pre-war days in Minas Tirith, the atmosphere was almost unbearably gloomy and dreadful. And he always remains optimistic until the final moment. When he thinks he's going to die, in the battle in front of the Black Gate, his last thoughts are simple and touching: "This is my story and it's ending now. Goodbye."
Of course this is as much a journey of growth and discovery for Pippin as it was for Frodo, though maybe on a smaller scale. (this is true of the other hobbits as well).
For me, the realisation that Pippin had really grown, not only in stature and courage but also in wisdom, came when he was infuriated by the ruffian's words to Frodo in 'Scouring of the Shire', remembering the events from the Field of Cormallen. He's come a long way from yelling 'Make way for Frodo, Lord of the Ring' in Rivendell.
Still, reasoning and choosing the best course of action logically is not really Pippin's strong point. Those things are much better acomplished by Merry.