Yeah, he knew you had being a singer for a few years but not to the point of APPEARING IN THE BARBIE MOVIE! And how he finds out about that? Well...

*Since childhood, Jason has always been a fan of Barbie, in secret ofcourse After being dead for years and revived he started dating you, who was a vigilante in Gotham since he was still a Robin and who sometimes helped him on patrols since this time. *

*When he found out that a Barbie movie was coming out he was VERY happy but he didn't show it as much because he wanted to seem serious around you, but, He could only see the film when it came out on TV for free because he didn't have time to go to the cinema and watch a film at night and still stand in line to get a ticket, no, he watched it in his super comfortable house and was loving the movie, even though he was watching it alone since you were at your parents' house. He was watching the movie until the end of the film that started playing the song 'What was i made for'? which was a super emotional scene, until he realized...YOUR VOICE! YOU WERE SINGING AT HIS FAVORITE MOVIE! After the film ended he went to YouTube and researched the lyrics of the song, he spent DAYS memorizing the lyrics.(

When you came home you were asleep on your bedroom until notice that he is not on your side and then you hear him in the living room singing your song 'What was i made for' VERY happy, almost jumping, you left the room and went to the living room, to see what he was exactly doing

"WHEN DID IT EEEEND? ALL THE ENJOYMEEEENT, IM SAD AGAAAAIN, DONT TELL MY BOYFRIEEEEND, ITS NOT WHAT HES MADE FOOOOR, WHAT WAS I MADE FOOOOR?"

He sang with his bottle of water while pretending it was a microphone