PHILADELPHIA (CBS) -- It was a big thank you from grateful parents of a little boy who's in Philadelphia while being treated for a rare kind of cancer. Last month, Jack Callahan sent a letter to Gritty, saying his biggest birthday wish was to meet the Flyers' mascot.
Jack got his wish Wednesday and now, his parents say they are forever grateful.
The day after his dream came true, Jack is playing and wearing his favorite Gritty T-shirt.
On his fourth birthday, Gritty visited Jack, who was also dressed up in his Gritty Halloween costume. It was a birthday wish come true for the little boy who's being treated for a rare kind of cancer at CHOP.
"He was happy enough to actually have a tear of joy, which for my wife and I was an awesome moment, because he's been through so much, and so many tears that were not joy over this last nine months. It was just amazing to see," Jack's dad, Michael Callahan, said.
Since moving to Philadelphia from Virginia for treatments, Jack has been intrigued by Gritty.
Last month, Jack dictated a letter to Gritty, saying he was his biggest fan and wanted to meet the fuzzy mascot for his birthday.
"I am your biggest fan in the world and I love you," Jack wrote to Gritty.
The Flyers sent the love back, delivering the popular googly-eyed mascot for Jack's birthday, along with presents and a customized No. 4 jersey.
The day after Jack's birthday, his parents wanted to share their gratitude.
"We really appreciate what the Flyers did and the Ronald McDonald House coordinated the birthday as well," Callahan said. "It was great. This is a place where people understand what Jack's going through, the other families understand and have so much empathy for each other."
Jack has had a stem cell transplant and is getting chemotherapy.
His parents say it's been a tough battle for the little boy but the distraction of Gritty has helped a lot.
And now his fourth birthday, with the guest star visit, will also be super special.
for more features.