you were just leaning your arms on the railing on the astronomy tower just minding my own business singing Accidentally in love by counting crows

You - “So she said, "What's the problem, baby?" What's the problem? I don't know Well, maybe I'm in love (love).

mattheo walks up behind you and starts singing with you

Mattheo - “Think about it every time I think about it. Can't stop thinking 'bout it”