Why (you, stand) ... on a chair when I (come) ... into the room?
were you standing, came
I (sit) ... in a cafe when you (call) ... .
was sitting, called
When I (walk) ... into the room, everyone (work) ... .
walked, was working
My dog (nap) ... when I (come) ... home
was napping, came
We (wait) ... on the platform when the train (get) ... to the station.
were waiting, got
When I (leave) ... the house, the sun (shine) ... brightly.
left, was shining
Tommy (watch) ... a film when he (hear) ... the noise.
was watching, heard
Everyone at the cafe (enjoy) ... their coffee, then the stranger (appear) ... .
was enjoying, appeared