They are voiced by Harvey Fierstein, Gedde Wantanabe, and Jerry Tondo, respectively in both films.
Like other newly recruited soldiers, they lacked military skills before they were trained. However, they were harder to train than most. Even Mulan learned faster than they. Eventually, their training paid off and the trio were capable fighters. Even so, they still had trouble doing things right and were rather clumsy. They served largely as the comic relief, often involving slapstick humor that made them reminiscent of the Three Stooges. Eventually, despite some early conflict, the three extended an open hand to Mulan and became her "army buddies", though they, like the rest of the army, thought she was a man named Ping. As soldiers, they each had a different color uniform: green for Mulan, red for Yao, yellow for Ling and blue for Chien-Po. Unlike most other soldiers, Yao, Ling and Chien-Po did not seem to think any less of her when they found out she was a woman. During the battle with the Huns they discovered that Ping is a woman named Mulan when Chi-Fu orders Shang to execute her they tried to stop him, only stopped by Chi-Fu who tells them that they knew the law. However Shang spares her instead for saving his life from the avalanche. When they arrived at the Imperial City they are shown along with the entire army saddened of leaving Mulan because of Chi-Fu. When they later met up, they even agreed to participate in her plan to stop the surviving Huns by disguising themselves as concubines. Somehow, they fooled the guards, though none of the three made a very attractive woman (especially Yao, as he kept his facial hair even in makeup).
In the second film, the three were given a more substantial role and are shown not to have changed since the first film. They had been to see the matchmaker that rejected Mulan in the first film, but she decided there could not be a match for any of them, and threw them out. They were discouraged, but felt better when Mulan and Li Shang came to recruit them for another mission. Shang claimed to the emperor that just the five of them would be enough protection for his three daughters. Although still as bumbling as ever, Shang knew that they were instrumental in their victory against the Huns, which they did not appear to have received the same credit for. They gladly joined the escort to get the emperor's daughters to the Qui Gong princes they are engaged to. Along the way, they develop feelings for the princesses. They take the princesses to a carnival for some amusement. Eventually, all three princesses admit that their feeling are mutual, and do not want to marry the princes, despite their duty. Mulan, knowing this, leaves the trio with the princesses, and goes to offer herself to the royal family instead. However, the trio arrives with the princesses, as does Shang. Mushu pretends to be the Great Golden Dragon of Unity who commands that they be allowed to marry whoever they want, allowing them to be with Yao, Ling and Chien-Po. Presumably they did marry, though nothing was shown to indicate this.
In Kingdom Hearts II, Yao, Ling and Chien-Po appear as minor characters in The Land of Dragons with pretty much the same role as they had in the original film: they, along with Mulan, are members of Li Shang's troop.