Mrs. Justin Bieber

Justin Bieber has plenty of superfans. But none are quite as special as Avalanna Routh, the 6-year-old known to her hundreds of thousands of Twitter followers as Mrs. Bieber.

Routh battled AT/RT, an atypical teratoid rhabdoid tumor – a rare form of brain cancer. But her struggle didn't stop her from adoring the teen idol – and making it known to friends and strangers alike that she planned to marry Justin Bieber one day. The Jimmy Fund caught wind of her love for Bieber and arranged a "wedding" for Routh at an event – and news of the faux-nuptials got back to Bieber.

Rather than rolling his eyes at a little girl's big dreams, Bieber gave Routh the greatest Valentine's Day present she could imagine, flying her and her family to New York to meet him. She later got to appear on stage with her hero. Bieber called Routh inspiring, saying that meeting her was the best thing he's done.

Avalanna Routh lost her fight Sept. 26, 2012, dying of the tumor she had struggled against. We're grateful to Justin Bieber for helping make her short life a very, very happy one.