[Pomegranate]

Oh, dear Legolas and his role as prince charming...

I also would have pointed out both of the two options Nog mentioned - Denethor and Isengard. Now, thinking about the definition of absurd as "Absurd (ridiculous, senseless, foolish)". Senseless - Denethor towards the end of his days, definitely losing his sense. Foolish? Saruman in his stony circle, assuming he could with the power of Isengard beat or even collaborate with the power of Mordor. There's a lot of absurdity in Bombadil, but I have to disagree him fitting with the latter two pieces of explanation.

"There and back again" - I love travelling too much to take it as absurd. Bilbo bought a lot back home from his trip, not only treasure but a broader understanding and stronger character. Not foolish or senseless, hardly even ridiculous.