Kelsey is fairly short when compared to her friends Craig and J.P. She has peach skin, light red hair tied into a bun at the back of her head, and thick, dark red eyebrows. She also has Mortimer, a yellow and green bird that sits on her head most of the time.
Kelsey wears a blue-gray T-shirt with a heart on it, and also wears pink shorts. In the pilot, her shoes are green and have a white bottom, but in the series, she wears blue boots. She has a dark blue cape that she wears around her neck.
Kelsey is very dramatic, in that she often narrates her life in her head in a style akin to theater.
She likes reading, as shown in "The Final Book" and is very upset when she can't find the last book in her favorite series. Kelsey says she spent years reading the young adult series and threatens the librarian when he says he can't tell Kelsey who took the book she's looking for. Kelsey's stated she "doesn't do sci-fi." She was very aggressive about finding her book.
- In "You're It", it is revealed that her father is the only parent for Kelsey. And considering Kelsey’s comment about being “half-orphan” in the episode “Kelsey Quest”, it’s to be assumed that her mother passed away, possibly when Kelsey was at a very young age. This assumption is proven in  when it is revealed that she did, in fact, pass away.
- Kelsey was and in some ways, still is, very close to her deceased mother. Her mother read her bedtime stories (which may have been the source of her love of books), and in "Alone Quest", Kelsey thanks her mother for the beautiful day.
- Kelsey is one of the only characters to be recast in the series, next to Earl Williams and Jessica Williams.
- In “The Invitation” Kelsey revealed the only dish she knew how to make was the Hungarian dish, Chicken Paprikash. This possibly means that Kelsey might be part Hungarian.
- In "Doorway to Helen" it is revealed that Kelsey is Jewish.
- In "Big Pinchy" it is revealed that she is camera-shy.
- In "The Takeout Mission" she mentioned that she is 8.
- Kelsey's voice actor, Cherami Leigh. is also known to provide the voices of  in 
- Kelsey does not share the same last name with her father, implying that Bern was her mother's maiden name.
- In "Alone Quest", it is revealed that Kelsey is writing a book, "Robyn and the Snow Sword", which is what has been hiding behind the door that says "Keep Out J.P.".
|1. "Itch To Explore":||Appears||17. "The Invitation":||Appears|
|2. "You're It":||Appears||18. "Vulture's Nest":||Appears|
|3. "Jessica Goes to the Creek":||Appears||19. "Kelsey Quest":||Appears|
|4. "The Final Book":||Appears||20. "Jpony":||Appears|
|5. "Too Many Treasures":||Appears||21. "Ace of Squares":||Appears|
|6. "Wildernessa":||Appears||22. "Doorway to Helen":||Appears|
|7. "Sunday Clothes":||Appears||23. "The Last Kid in the Creek":||Appears|
|8. "Escape from Family Dinner":||Appears||24. "The Climb":||Appears|
|9. "Monster in the Garden":||Appears||25. "Big Pinchy":||Appears|
|10. "The Curse":||Appears||26. "The Kid from 3030":||Absent|
|11. "Dog Decider":||Appears||27. "Power Punchers":||Absent|
|12. "Bring Out Your Beast":||Appears||28. "Creek Cart Racers":||Absent|
|13. "Lost in the Sewer":||Appears||29. "Secret Book Club":||Absent|
|14. "The Future is Cardboard":||Appears|
|15. "The Brood":||Appears|
|16. "Under the Overpass":||Appears|
|Craig of the CreekCharacters in|
|Main characters||Craig • J.P. • Kelsey • Mortimer|
|Supporting characters|| Williams family: Bernard • Duane • Earl • Jessica • Jojo • Carter Brown
Mercer family: Laura Mercer
Bern family: Mr. Bern
Creek kids: 10 Speeds (Handlebarb, Warpspeed, Todd, Cannonball) • Horse Girls (Mackenzie, Melissa, Maney, Marie) • Junk Lord • Kit • Sewer Kids (The Sewer Queen, Frisboy, Scuba, AquaTina, Tiny Trunks, Speedicous) • Stacks • The Elders (Barry, Mark, David) • The Junior Forest Scouts (Jason, Tony, Boris) • The Ninja Kids (Yustice, Zatch, Prinda) • The Paintballers (Paintball Mike, Paintball Benny) • The Scratchless • The Witches of the Creek (Tabitha, Courtney) • Wildernessa • Cheesesticks • Tea Timers (Eliza, Jane, George) • Toman