The Surprise Proposal

My fiance thinks she's going to watch Despicable Me 2 on a lazy Saturday afternoon. As the first fake trailer is played, she is mostly engrossed by an article on her phone about how to get rich quick. Then one of our favourite songs comes on and she slightly glances up but is still consumed by the article. However, she eventally looks up and realises the person on the screen is someone familiar..
Please note: I don't have a musical bone in my body.