From PEOPLE Magazine Click to enlarge
Dear Zac, Thank you for the best experience of my life. Now I know that dreams do come true. Love, Dayana." Zac Efron is proudly holding a trophy engraved with those words—a gift from a young fan at a Make-A-Wish Foundation event in L.A. on Aug. 23. "Oh my gosh, this is gorgeous—I can't believe you did this," he says to Dayana, his eyes welling up. "Thank you so much."

For the High School Musical cast, the opportunity to give back to fans has been its own reward. From Make-A-Wish to Feeding America to St. Jude Children's Hospital, the HSM stars have brightened the lives of children across the country. "It's a very humbling experience," Efron says of working with the Make-A-Wish children, all of whom are coping with life-threatening medical conditions. "The fact that for a minute we can let them forget about whatever issues they are currently going through and take them into the High School Musical world, which is more carefree and fun. That's a pretty thrilling aspect of it."

Naturally, the kids are pretty thrilled themselves. "The High School Musical cast always treats the kids like VIPs," says Brent Goodrich, spokesman for the Make-A-Wish foundation. "It's something the kids carry with them for a long time afterwards." Upon meeting her idol Zac, "I was really freaking out and shaking!" says Anna, 11, who battles a condition that prevents her body from metabolizing some proteins. "I am really glad I met him. He makes me so happy."

Those are the moments that mean the most, says Ashley Tisdale, who is also active with Make-A-Wish. The kids "have such amazing spirits and their personalities are so beautiful," says Tisdale, recalling an especially memorable encounter with a spunky little girl during a set visit on HSM3. "Everyone was like, 'She loves you, Ashley. She wants to meet Sharpay,'" says Tisdale. "So I went down there and I had my dog Maui with me and the little girl, all she wanted was to be with Maui! It was all about my dog!"

For Monique Coleman, giving back means setting a good example for fans. "I wanted to show that I stand for something more important than what I am doing on the screen," says the star, who is raising awareness of childhood hunger in the U.S. as an active supporter of Feeding America.

Some of the work can be heartbreaking. Corbin Bleu recalls meeting with a young girl on the set of HSM3 who died of cancer soon after. "Her family sent me a letter thanking me for spending time with her and saying that some of her last moments were really wonderful because of it," says Bleu, who is involved with the Starlight Children's Foundation. "It showed me that time is so crucial."

It's a lesson that all of the HSM stars carry with them, along with the memories of the kids whose lives they touch—and who inspire them right back. "It's nice that we can make these kids forget what their life is like for a couple minutes," says Tisdale. "That's what gets me thinking, 'Oh yeah, that's why I do this.'"