Charles Tillman has become one of the most popular players in Chicago Bears history, adored by fans and respected by teammates and opponents alike. But it wasn’t always that way.

Growing up in a military family, Tillman attended 11 different schools from kindergarten through high school. Moving around so much, he felt as if he never fit in and was bullied by other kids.

Tillman recently shared that experience—and helped support a 16-year-old girl who is in a similar situation—as part of a documentary on USA Network. “NFL Characters Unite” profiled NFL stars discussing their own personal stories of overcoming prejudice, bullying and discrimination with the goal of helping young people who are currently facing the same types of challenges.

“My dad was in the military so you move every other year,” Tillman said in the documentary. “I went to third grade from Kansas to a small base in Germany. You’ve got to make new friends. 

“The kids who do the bullying really don’t understand what you go through moving from place to place. I didn’t really fit in. I was labeled as the geek, the loser. That was probably one of the hardest struggles I had to go through.”

Those difficult memories enabled Tillman to empathize with Katy Stephens, a high school student who also has been moving frequently because she’s part of a military family. 

Katy’s latest move took her to Chicago, where she joined a theater program at her new school but eventually quit because she was being bullied by other girls. She was made to feel like an outcast and that she wasn’t as good as the other kids.

“It was a really hard choice to drop acting because it’s what I love,” she said. “I didn’t feel accepted. I didn’t want to be in that environment.”

It was at that point that Tillman stepped in to encourage Katy not to give up on her dreams.

“They took something you love and they made you quit,” Tillman said to the 16-year-old. “You can’t let someone take something away from you. People said I’m old and I shouldn’t play in this league. I love to prove people wrong. It starts with you believing what you want to do.”

Tillman then surprised Katy by taking her to the Second City, a world famous improvisational company that spawned the careers of legendary actors such as John Belushi, Dan Aykroyd, Bill Murray, Chris Farley and Julia Louis-Dreyfus.

At Second City, Katy participated in an improv class and performed in front of a live audience. Moving forward, she will continue to take an acting class as well.

“When I was up on the stage, it wasn’t like anything I’ve ever experienced,” Katy said. “I felt a power, like I can do things and I’m going to do these things. To be so accepted, it made me feel great inside.”

Tillman was pleased that he helped convince Katy to continue to chase her dreams.

“If I can have a smidgen of influence on Katy,” Tillman said, “well hey, I’ve done my job.”

Other pro football stars who are featured in the NFL Characters Unite documentary include Packers receiver Randall Cobb, Giants receiver Victor Cruz, Giants linebacker Mark Herzlich, Jets center Nick Mangold, Ravens running back Ray Rice and Texans defensive end J.J. Watt.