Crossword puzzle clue "they pop up now and then"

They pop up now and then

Hybrid car that runs a few seconds, then stops, then runs again, then stops again...?

1950s-'60s hit with the lyric "Ah, you made me love you / Now, now, now, now your man is come"

Flicker ... pop ... pop ... pop

Exams that used to go up to 1600 and then 2400 and now I can't keep track: Abbr.

Do this, then that, then this again

Place whose population was 1, then 2, then 0

Back then, back then