hit it off

listen to the pronunciation of hit it off
English - English
To develop an amicable relationship (with), especially in a sudden manner during an initial encounter

Those two are really hitting it off. I wouldn't be surprised if they started dating soon.

(deyim) (hit it off with) Be naturally friendly or well suited
get along well, be compatible for one another
hit off
describe or represent accurately; produce readily, produce offhand
hit it off