when he's, it's, etc. at home?

who's (someone) when (he's/she's/they're) at home

humorous Who is that person? Primarily heard in UK. Robert De Niro? Who's he when he's at home? I've never heard of that actress before, who's she when she's at home?
See also: home
Farlex Dictionary of Idioms.

when he’s, it’s, etc. at home?

(British English, informal, humorous) used to emphasize a question about somebody/something: ‘Shirley Hills wants to meet you.’ ‘Who’s she when she’s at home?’
Farlex Partner Idioms Dictionary
See also:
  • who's (someone) when (he's/she's/they're) at home
  • who's someone when they're at home
  • What's (something) when it's at home?
  • cloth ears
  • good on (someone)
  • good on you
  • good on you!
  • chip
  • chips
  • not a sausage