어라 그러다

quoting someone's order: 'do it'

-아라/어라 is the blunt command form, and 그러다 after it stands in for 'say so', reporting the order without the full 라고 하다. So 노래 한번 불러 봐라 그러는데 is 'they say sing us a song', and 10억이면 부모님도 가라 그럴 거야 is 'for a billion won even my parents would tell me to go'. The full form -(으)라고 하다 means the same thing; dropping 라고 in favour of 그러다 is what makes this the spoken version.

Register: casual spoken