“I was always the shortest boy in my class.”

“I thought something was wrong with me.”

These are just a few of the things that kids have to say about bullying, a subject that hurts so many kids. Their voices are part of a new special on the subject.

The documentary “Speak Up” will be shown on Sunday on Cartoon Network at 5:30 and 8 p.m. President Barack Obama has taped an introduction to the show.

Athletes and performers including former NBA star Chris Webber, tennis champion Venus Williams and NASCAR driver Trevor Bayne, talk about their own experiences being bullied.

They also offer advice, aimed not just at kids who are being bullied but also at kids who want to help a classmate who is being picked on. “You can walk someone to class . . . you can ask them if they’re okay. . . . We’re all on the same team,” Webber tells kids.