Humbah was created by the Teletubbies when they needed help. She actually wasn't the first one made, and Dipsy wanted her to be green, as he created them and wanted the first to be his. But, she came out yellow, so she became Laa-Laa's instead, and Dipsy got stuck with Jumbah by lottery. She is very evil due to the evilness that was added when she was created.
Humbah's Adventure was a shame made for her, but when she was shown it, she just spat on it and walked away. Probably because it involved her getting hit a lot. One of the reasons she hates humans so much is because of that shame.
Once, she tried to rebel against the Teletubbies single-handed, but they used the self destruct chip in her, and she exploded. Fortunately, they made her bomb-proof, so she was unconscious for several hours, and then promised that she would never attempt to harm the Teletubbies again (a promise that was not kept). She also has Heterochromia, a syndrome where her eyes are different colors, green and red, respectively. Humbah's UnRank is 439. Which means she is not a moron, but is almost a moron. She also lost some of her Heterochromia because of the 1:2:1 ratio in the F2 generation.