The Tosefta (Hagigah 1:2) says that a child who is old enough to eat a ke-zayit (measure of an egg) of roasted meat is obligated in the korban.
James Frazer thought that the korban Pesach was related to some early form of human sacrifice. Of course, Frazer saw human sacrifice lurking around every corner (and wasn’t one for double checking facts) and scholars today discount this idea.
Marcus, consul of Jerusalem for Rome in the time of Bayit Sheni (the second Temple) remarked to the Kohanim that it was "neither seemly nor polite" that important people did not get "cuts" in line to bring the Karban Pesach. The Kohanim replied that everyone was equal in the eyes of G-d. (This account is a mixture of fact and fantasy. I don't know what category this particular tale falls into.) (Ibn Verga)
Conversos of Spain and Portugal would often eat an entire roast sheep on Pesach. (Shauss)
The Zohar notes that karban is roasted since the sheep was worshipped by the Egyptians and there is a halakhah that idols should be burnt. (Midrash Says)
R. Levi of Berditchov says that the real miracle of Pesach is that the Jews had the courage to slaughter the sheep worshipped by the Egyptians. It is surprise that G-d, the creator of the universe can perform a miracle, but this act of courage of the Israelites is indeed miraculous. (Schocken)
The Mekhilta de Rabi Yishmael at one point suggests that as soon as someone converts to Judaism, they should immediately bring the karban Pesach. Although the Mekhilta later rejects this idea, the fact that it was even suggested underscores the importance of the karban Pesach. Both the first Pesach and the Pesach with Joshua at Gilgal contain elements of conversion. At both points the men are circumcised and the Israelites miraculously cross a body of water which can be seen as representing mikvah. (Yosef Carmel)