Justin Bieber proved just how sweet he can be when he surprised two very lucky and deserving fans, The Wrap reported. On Fox's new show "Knock Knock Live," Bieber granted a birthday wish to a teen who beat cancer and visited a toddler with Down syndrome.

For his first surprise, Bieber visited Ashley, a 15-year-old cancer survivor. Doctors told Ashley she might not survive, and her illness forced her to skip her quinceañera, a tradition that celebrates the transition into womanhood. Ashley credits Bieber's song "Pray" with giving her the strength to beat cancer.

Bieber arrived at her house with dress options, and Ashley looked pretty in pink with her choice of a sparkly, ruffled ball gown. He led her to an undisclosed location and held the car door open for her in perfectly gentlemanly etiquette.

"This is like a fairytale come true," Ashley said.

"Well you're the princess, I'll be your prince charming," Bieber replied.

When they arrived at the location, a beautifully decorated banquet room awaited Ashley. She was able to make up on missing out on her quinceañera when she was ill and she slow-danced to "Pray" with Bieber.

The pop star's next stop was to a church where little Noah and his dad Nikia were congregated. Noah was diagnosed with Down syndrome, and doctors told Nikia that his child would never walk or talk, according to Ryan Seacrest.com.

The tot beat the odds and displayed his skills as he acted as his dad's hype man while performing for Bieber on the church's stage. Bieber then blessed the family with a $50,000 check. Nikia and his wife broke down in tears.

"Man, such an amazing guy," Nikia said on camera. "It's so funny how the media portrays people and then when you meet them for yourself, they're the exact opposite of what you've been told that they were."

Check out the clips with Ashley and Noah here.