- "Rosie too!"
- —Rosie's catchphrase
|Age|| Newborn (Big Brother Caillou)|
~1 (some season 1 episodes)
2 (rest of the series)
|Family||Caillou (brother), Doris (mother), Boris (father), Gilbert (cat), Rosemary (grandmother), Hadley (grandfather)|
Rosie is Caillou's 2 year old sister. In the French novels by Christine L'Heureux that the show is based on, her name is Moussline. She is also the daughter of Boris and Doris and the granddaughter of Rosemary and Hadley.
Rosie has orange hair which was at her shortest in Big Brother Caillou since she was born. But, as she grew older, her hair grew a little fuller.
Rosie wore yellow long-sleeved zipper-front footie pajamas with a red zipper as a newborn. In various episodes of season 1 and a flashback in new member of the family, Rosie wore a yellow long-sleeved white collared pajama shirt with a zipper accompanied by yellow pajama pants and pair of red baby booties. However, in most episodes, Rosie wears a teal long-sleeved calf-length dress with a whitish yellow collar and a matching colored sash, red ankle-high socks, blue strapped Mary Jane shoes, diapers in the first two seasons, then frilly blue panties from season 3 onward.
- Rosie tends to cry over almost anything usually resulting in her needing to be comforted by either parent, yet she can laugh at anything she sees as funny.
- Caillou usually shows love to Rosie despite some quarrels between the two. In the episodes "Halloween" and "Caillou's a clown", she was coulrophobic or afraid of clowns, but he was able to convince her to not be afraid of them.
- She can talk as well Caillou can usually just short sentences some even being one word or a sound effect plus speaking in the third person most of the time. She always says her name, Rosie.
- It is shown in "Olive Muddle" that Rosie likes olives.
- Rosie's favorite song is "Ring Around the Rosie".
- Rosie does not like beans, as shown in the episode "Caillou becomes a waiter".
- She's developed a lot in the later seasons. In "Caillou Helps Out", Rosie starts teething, and in "Am I Big Yet?" She goes through a growth spout. From season 3 onward, she was in potty training.
- Her first appearance was in "Caillou Makes Cookies" and her last appearance was in "Soccer Trouble".
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