dream up
US /ˌdriːm ˈʌp/
UK /ˌdriːm ˈʌp/

1.
idear, inventar, imaginar
to invent something in your mind, especially something unusual or impractical
:
•
He dreamed up a crazy plan to travel around the world in a hot air balloon.
Él ideó un plan descabellado para viajar alrededor del mundo en un globo aerostático.
•
Where did you dream up that ridiculous idea?
¿De dónde sacaste esa idea ridícula?