"Blue's Clues" star Steve Burns unlocked a memory buried deep inside when a cancer survivor visited him at a convention -- turns out they'd met 2 decades earlier thanks to the Make-A-Wish foundation.
Brandon Ragland tells TMZ ... he's been in remission for more than 23 years and recently reconnected with Steve at Steel City Con in Pennsylvania, some 22 years after their first face-to-face under much different circumstances.
It's pretty cool ... Brandon says he walked up to Steve's booth, shook the actor's hand and pulled out a picture of the 2 of them from 2000 -- back when Steve was a Make-A-Wish kid -- and it all clicked for Steve, whose eyes lit up and said, "I remember this and you!"
Brandon says Steve told him a story about their first encounter at Serendipity 3 in NYC. Brandon was a 4-year-old meeting his fave TV star, and Steve recalls him being a wild child running around the restaurant.
During their reunion, Steve asked Brandon for a new pic together, and then they both started crying. You can understand why all the water works -- Brandon had stage 4 cancer in his kidneys and lungs when they first met, and now he's 25 with a family of his own.
Brandon says Steve then pulled him in for a hug and said, "This made my entire year and I'm so glad you're here."
Since then, they've stayed in touch on social media ... and Steve's made it clear how proud he is that Brandon's now a healthy father and husband.
BTW, their OG Make-A-Wish experience back in the day included dinner with Steve, a Toys "R" Us shopping spree ... and tickets to "Blue's Clues Live" in NYC.