"I'm sittin' under this digital tree!"
He and his brother Fred are generally inactive, and constantly like to make note on how they're just sitting in front of the digital tree in their family's backyard, much to the annoyance of their sister Amanda.
Their life takes a turning point, though, when they by chance get a visit from the younger-aged versions of their uncles Phineas and Ferb. After the aforementioned visit, Xavier and Fred construct bumper cars that can move in five dimensions, but they still answer Amanda's query about their activities with "Nothing" ("Phineas and Ferb's Quantum Boogaloo").
Xavier and Fred are as bright and creative, and build impossible stuff just like Phineas and Ferb, although it took the younger version of their uncles to bring it out of them.
Xavier looks quite similar to Jeremy, having blond hair, bright blue eyes, and a similar face shape. He wears a white T-shirt with brown stripes and green shoulders, green pants, and red sneakers with white lining. It was later confirmed by Dan Povenmire that Jeremy and Candace end up staying together, thus confirming that Johnson is the father of Xavier.
- "Xavier" and "Amanda" are the two names that Candace had picked out for her future children, as seen in "The Best Lazy Day Ever", "Swiss Family Phineas", and "Spa Day". Given her interest in Jeremy, it is highly likely that he is their father. Genetic evidence supports this as well, as he has the same blonde hair and light blue eyes as Jeremy.
- Xavier's, Fred's, and Amanda's situation is analogous to Phineas, Ferb's, and Candace's except rather than trying to "bust" her brothers for doing something, Amanda tries to bust Xavier and Fred for doing nothing. This being the case, Xavier resembles Phineas as he talks more and tells Fred that he likes Phineas while Fred says that he likes Ferb.
- It is worth noting that Xavier and Fred were not originally interested in creating things, until Phineas and Ferb gave them the idea to create 5th dimensional bumper cars.
- Isabella finds out that she is the future aunt to Amanda, and likewise, Xavier. This means she is likely going to marry either Phineas or Ferb.
- The episode "Act Your Age" confirmed that Phineas and Isabella start dating in the future. Thus, it is almost certain that she will marry Phineas and not Ferb.
- In the Dutch version of Phineas and Ferb, Xavier is voiced by the winner of the Junior Eurovision Song Contest 2009, Ralf Mackenbach.
- "Phineas and Ferb's Quantum Boogaloo" (First appearance)
|Phineas Flynn | Linda Flynn | Candace Flynn | Clyde Flynn | Betty Jo Flynn | Lorraine | Xavier | Fred | Amanda|
|Perry the Platypus | Steve | Goldie | Bucky†|