Despite her always optimistic and cheerful attitude as well as an ever-lasting smile, she is not to be undermined for her ability to extort parents for their time or money.
Principal Thomas first appeared during the ending credits of Home Sweet Home-School, where Jessica was visiting her office with Evan and Emery. Jessica was concerned because the grades on their report cards were nothing but a bunch of colorful stickers or rainbows and bunnies and things along those lines. Principal Thomas was seen, sitting there, rambling on and on, telling her about how all of those stickers were special and amazing in one way or another, which left Jessica confused and concerned about her sanity. She told the kids that she was crazy in Mandarin and Emery translated that to her, telling her that she likes her. Principal Thomas responded, by thanking her, by bowing and putting her hands together.
Principal Thomas appeared again in Dribbling Tiger, Bounce Pass Dragon, where she called Louis and Jessica into her office to tell them that they were in trouble for not attending any extra-curricular activities. Because the parents at extra-curricular activities were all white American, Thomas aimed to expand racial diversity of the parental contribution (which means that Louis and Jessica are being forced to either pay or volunteer just for being Asian). Jessica hated the idea of having to do this and she opposed to the idea, unfortunately the only other option was to donate money to them and so they both immediately agreed to after school activities. Jessica came to support the kids in the school play. Principal Thomas showed that the play was written by herself and it was all about tolerance and acceptance and it was the most happy and wonderful play there was. Jessica rewrote the entire story to teach people being an actor is a very dark turn to take in life, which Principal Thomas hated. When confronted with this, Jessica rebelled against her and stood by her point, which led to her getting exempt from the activity which is really what she wanted in the first place.
In the episode The Real Santa, she hosted the Palms Elementary holiday play. However, she didn't want to do anything Christmas related, trying to be sensitive to all people who didn't practice Christianity. So, the entire play was very bland and almost entirely deprived of substance and content, having only one character. Panny, the Pancultural Seasonal Entity. This play received a lot of hate because it was boring and pathetic, and it came to the point where the audience started chasing Panny though the basketball courts so they could beat him.
Principal Thomas is very overly happy to the point of fanaticism. She tries too hard to be politically correct, doing everything she can to avoid doing anything even the slightest bit racist, in order to try and make all other races feel comfortable. This kind of behavior is taken to extremes as she her attempts to be politically correct, have the tendency to actually do come across as absent-mindedly offensive. In fact, she cares so deeply about people's feelings that she doesn't care about their finances or busy lives.