Katy REJECTS fan's proposal: 'I'm dating someone' - WATCH

Katy Perry, currently on her Lifetimes Tour, publicly rejected a marriage proposal in Prague, humorously stating she's already dating someone. This comes as her relationship with Justin Trudeau has become increasingly public, with the couple recently stepping out together and making their romance Instagram official. Trudeau even paid tribute to Perry by dressing as 'Left-Shark' for Halloween.