Archive Panic: Besides the original books, there are also 14 years worth of television episodes, 1 theatrical movie, 5 direct-to-video movies, a few shorts and TV specials, and a video game for the Nintendo GameCube. Good luck trying to get through it all.
Cant Unhear It: Even though Will Ferrell is the original voice of Ted, Jeff Bennett is often thought of as the definitive voice for the character due to how many times he voiced him. This also applies to Frank Welker as George, since he voiced him in all projects.
Specifically Swedes (got his own adaptation there), Japanese and Australians (both for the TV series).
Japan is an especially noteworthy case. Not only is it constantly in the top 10 animated TV show ranking for the country every week (which is mostly domestic animation), but the show increased the popularity of the name George in the country (this unusual as traditional names are more common in Japan than Western ones).
"George and Jumpy played nut hockey until the sun went down."
"George had to find a way to help the Chef with his weed problem."
Adaptation Displacement: Though the books may be more well-known, this series displaces the original line of shorts made in 1980.
The series is based on the 2006 film, but while that movie did relatively well and earned five sequels, the TV series is better remembered, likely because it's been running since 2006.
Awesome Music: You simply can't go wrong when Dr. John composes your theme song.
From the 80's series: "Curious George, the curious little monkey..."
Accidental Aesop: The ether scene in Curious George Takes a Job is Played for Laughs and George recovers easily from the incident, but this article posits that the scene could be used as a way to teach children to not to touch or smell substances they don't recognize and could end up getting hurt or sick from (and for their parents to keep said substances out of their reach!).
Accidental Innuendo: In Curious George Goes To The Laundromat, the Man in the Yellow Hat threatens to spank his monkey.
Big-Lipped Alligator Moment: The infamous ether scene◊ in Curious George Takes a Job. George, curious as ever, uncorks a bottle of ether at the hospital he is at to smell its contents, and then immediately begins tripping out before falling unconscious onto the floor. The Man in the Yellow Hat, the doctor, and the nurse find him this way and wake him up in the shower (much to George's confusion). Unlike a lot of the other things George does throughout the book, the ether scene does not come up again and exists mainly as just a short gag.
The original book depicts George smoking The Man In The Yellow Hat's pipe with no ill effects. Becomes a case of Values Resonance in the 1982 Stop Motion special where George tries the pipe and hates it, convincing The Man In The Yellow Hat to give up smoking in the process.
The Man In The Yellow Hat threatens to spank George in the animated short "Curious George at the Laundromat". That would come across as flat-out animal abuse today in an era where spanking was already a controversial form of discipline, even in 1980. When the episode was adapted into a picture book, The Man In The Yellow Hat instead says, "There you are, George. You've caused a lot of trouble. I'm taking you home."