Cassie Williams and Zeke are freelance spies.
Well, they do not actually do this for money, mostly for fun and because someone has to do it
Cassie is a Super Sleuth when we meet her in the first recorded adventures. We know this because the narrative specifically says so, complete with capital letters. It tells us that as she is skulking around the playground at Hillsdale Elementary School where she, at 10 years of age, is a 5th grader. According to classmate - and ever-present problem in Cassie's life - Marilee, they should be behaving more maturely since they are the senor class at the facility and need to set an example, not "spying on people for as long as I've known you". Cassie chose to ignore her and just go on snooping with the help of her new Super Deluxe Spy Kit - a present from her parents - and be joined as always in her spy work by her bestie, Melinda. Unfortunately, Melinda had been turned to the other side by Marilee over the summer and was now dressed in - gasp! - a dress!
For informational purposes, it is important to point out that Cassie is a very pretty girl with blonde hair reaching past her shoulders. She, as you can tell by her reaction above, eschews frilly things and loves her jeans and work shirt which can take the strain of the kind of places that Cassie will inhabit to continue her endless espionage.
Zeke is not a spy. Well, not when we first meet him but once Cassie gets into contact, he will grow to like the excitement and join her. Before that, he is pretty much it seems a typical boy roughly the same age as Cassie. Bald headed, of course, with incredibly long fingernails (a foot!) and green skin. Yep, green. That was Williams' second clue about Zeke and his parents, Mirac and Inora were from another planet. The first was the space ship she saw them land in out in a clearing in the woods a short distance from her home. Before I go any further, though, it is important to note that Zeke and family are not really green-skinned. They had applied green makeup before meeting their first human because they had intel that reported all humans were colored green. Why they thought that in a moment.
Zekephlon is the full name of the young visitor from Triminica. That's not the name of a city or a state or a country. It is a planet. Obviously different from Earth and not even in the stellar neighborhood. They were on their way to a vacation spot on the planet Clurigan when their ship's computers malfunctioned and they landed in the first habitable space they came to. As you have gathered, the first human they meet is the snoopy Williams and they spend several hours in the night exchanging info about each other. That was when Williams learned she had a kindred spirit in Zeke as he is in training to attend the Interstellar Space Academy when he is a bit older.
So, To repair the damage, Zeke's parents have to head to the volcanoes of Hawai'i to get iridium. Meanwhile, Zeke is staying near the spaceship to help guard it. And he is going to cut his super-long fingernails and wear a wig and enroll in the school Cassie belongs to and that is how she and Zeke become partners in spying. Eventually they will even start their own intelligence company, Spies, Inc.
One final tidbit. The reason for the misinformation about humans being green is Robot. That's what they call the robot; Robot. Pretty straightforward and easy to understand why. Robot is described as "an incredibly ugly creature made of blue metallic coils" with "huge bulging eye sockets that had no eyes" - it is informative, occasionally helpful, and periodically disobedient, and more than a few times wrong. Like humans being green.