A Washington State high school student battling an aggressive brain tumor got the surprise of his life when a Seattle Seahawks player fresh off a Super Bowl victory made a special visit to his high school.

Doug Baldwin, a Seahawks wide receiver, snuck in a side entrance at Decatur High School in Federal Way, Wash., on Thursday night and spoke to an overflow crowd at the school's gymnasium about Dom Cooks, an 18-year-old senior at the school who was a standout football player before being diagnosed with a brain tumor two years ago that has left him confined mostly to a wheelchair.

"He spoke for about how he had met Dom when a local TV station had taken Dom to a regular season Seahawks game and how Dom had inspired him and so he rearranged his schedule so he could be there," said Decatur High School principal David Brower. "It was amazing."

It was Brower's idea to hold the early graduation ceremony for Cooks and his twin sister, Diamond.

"Dom always tells me that tomorrow is not a promise and so thinking of that reminder, we knew we had today and that today we could do a graduation," Brower said.

Brower and school officials put together the nearly 90-minute graduation ceremony in a week's time, and included Diamond at the request of her brother, whose tumor has recently grown and spread throughout his brain.

"They've been together in life and he didn't want to be alone at graduation, Brower said. "He wanted her to be with him."

The graduation ceremony, attended by at least 70 members of the Cooks' family, according to Brower, featured teachers selected by the siblings to speak, as well as the school's senior class president, who always speaks at graduation.

The ceremony also included a lot of humor, which Brower says is a trademark of Cooks, who could not be reached today by ABCNews.com.

"He was dancing and when a teacher started to cry, he said, 'Ah, don't you do that,' and started to mimic her crying," Brower said. "Dom took the microphone after accepting his diploma and was like a rock star."

"He actually said, 'I feel like a rap star with the microphone in my hand,'" Brower said.

When Cooks went to accept his diploma from the superintendent, he got out of his wheelchair but had some difficulty making it to the stage, according to Brower.

It was Baldwin, he says, who stepped up to help Cooks make his way up to the stage.

"And then he just quietly backed away as Dom took center stage," Brower said.

"This is a memory that Dom and Diamond and their family will have forever," he added. "They will know that on Feb. 20, the community came together and gave them all the love and support they deserve."