あの子はなんていたずらなのだ。

that (someone or something distant from both speaker and listener, or situation unfamiliar to both speaker and listener)

child; young (animal); young woman; young geisha; offshoot; interest; new shares; player who is not a dealer (in cards, mahjong, etc.); bird egg; -er (often of young women)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

such as; (things) like; exclamation

mischief; prank; trick; practical joke; pastime; hobby; playing with (a lighter, etc.); fooling around with; messing around with; amusing oneself with; tampering with; lewd behaviour; sexual misconduct; sexual assault; molestation; rape

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

be; is; indicates past or completed action; indicates light imperative