何してたんだ

what were you doing?

→ 何
phrase Rare #41,593
what were you doing? Casual and sometimes blunt; the tone can sound questioning or accusatory depending on context.
JA: 昨日の夜、何してたんだ?
EN: What were you doing last night?

で、お前ら何してたんだ?

So, what were you guys doing?

— ミスティック・リバー (2003)

何してたんだ?

What were you doing?

— ニュー・シネマ・パラダイス (1988)

今まで何してたんだよ

What have you been doing all this time?

— 天気の子 (2019)

暇なときは何してたんだ?

What did you do in your free time?

— ザ・マン・フロム・アース (2007)