何故登るのか。　そこにヤマがあるからさ

guessing Puru-see is meeting shiki today.

Oh man, this is such a great pun that I feel bad explaining it, but:

George Mallory, the first person to (maybe) reach the summit of Mount Everest, has been famously reported to have answered the question "Why do you want to climb Mount Everest?" with "Because it's there." In the Japanese translation that has stuck in the mind of the populus, however, the quote is altered to include the word mountain, i.e. "Because the mountain is there." And the Japanese word for mountain is... yama (やま, 山).

Thus:

Why do you climb?

Because the yama is there.

The expression tells me that Parsee ISN'T just plain nervous and fritzy today. That's precious! She actually appears to be enjoying herself. ^_^