It's a two-headed monster!
Taro-wa [[[dare-ga neko-o turete kita] -no] -ga nigedasita ka] sitte iru.
Taro-TOP who-NOM cat-ACC brought along NM NOM ran away Q know.
Lit. "Taro knows who(x) brought along a cat and that the cat that x brought along ran away."
Of particular interest to me is the nesting of relative clauses here. We have our most embedded clause, "dare-ga neko-o turete kita." This clause then merges with a matrix clause, "... -ga nigedasita ka." In this matrix verb, neko is interpreted as the subject of "nigedasita." However, this is further embedded in another matrix clause, "Taro wa ... sitte iru." Oddly enough in this one, dare "who" is interpreted as the object of "sitte iru!" The innermost embedded clause provides two separate heads for two successive matrix clauses!
Has anyone ever seen data like this from any other language? This is particularly complicated by the fact that the above example is a head-internal relative, and not an English-style external relative (I can't even think of an equivalent English example). I'm quite curious as to what is going on here.