This is apparently a meme called うんち提案おじさん or "Poop Proposal Man".

"Unchi shite?" (Will you poop?)

"Iya desu." (No/I find it detestable.)

"Nande? (chitsui)" (Why? (Murderous Intent))

http://www.pixiv.net/search.php?s_mode=s_tag_full&word=%E3%81%86%E3%82%93%E3%81%A1%E6%8F%90%E6%A1%88%E3%81%8A%E3%81%98%E3%81%95%E3%82%93

There's one with Captain Falcon and the dude is asking him "Will you punch?" instead.

Vid-szhite said:

This is apparently a meme called うんち提案おじさん or "Poop Proposal Man".

Alright, looks like we're in the weird part of the memeworld.