Mark: You were making breakfast and you thought he was in bed when you felt eyes staring at you. He caught you singing to y/f/s. He joined in.

Jack: He was recording a video and he had asked you if you saw his spare controller as his had stopped working. You couldn't hear him and were to into the musical your were singing to. When he noticed he left you alone and found it himself

Nate: He had walked into the living room to see you dancing to one of his songs he started singing and you had fun with it.

Razz: he dances with you when he finds you dancing 

Matpat: he asked you for an idea for a theory and instead found you singing loudly to you favorite fall out boy song.

Tyler: He wasn't expecting you to be quite the dancer but you were he found you jamming out to some panic! at the disco.

Will: he found out you could sing because you were singing one of his songs

Robert: you were a dancer in a music video and he caught you practicing 

David: You and the others were hanging out at a party of course David was vlogging everything you and Zane were completely drunk and singing karaoke at the bar