List of characters

Main Characters
These characters have all had a major role in the story of the show. Most, if not all of them, have appeared in the majority of series.

Major Characters
These characters often play major role in the story, oftentimes having several episodes that focus entirely on them, but are not always guaranteed to appear. They often play supporting roles in episodes they aren't the central focus on.

"Arc" Characters
These are characters that only make a few appearances, but play a major role in those few episodes. Their subsequent appearances after their debut are generally "sequels" to their debut, or closely connected. (Ex. A wish of Timmy's comes back for revenge in a later episode). They rarely appear unless they are a central focus, other than a cameo.

Supporting Characters
These are recurring characters that have appeared in a handful of episodes, but rarely do they ever have any major effect on the plot, and typically serve as background/group shot fodder.

One-Time Characters
These are characters that have only appeared in one episode, but played a major or supporting role in their lone appearance. Some of them have also appeared in other episodes in background shots.

'''This is a very long list. click on the show button to bring it up.'''

Background/Bit Characters
These are characters that have only made a few appearances, usually as a bit characters, and have little effect on the story. This also includes one-time characters who were not major characters in an episode, often only appearing for a one off gag.

'''This is a very long list. click on the show button to bring it up.'''

Alternate forms
Several alternate forms have appeared of the characters, usually as a direct result of wishing.

Crash Nebula
These are one-time characters that appeared in the show-within-a-show spin-off, "Crash Nebula", which was broadcast as part of Season 5. However, the spin-off was never picked up as a series by Nickelodeon, and none of these characters have appeared since.

Live action
The tenth year anniversary special "A Fairly Odd Movie: Grow Up, Timmy Turner!" are played by live action characters. Thirteen years have passed since the main series, and everyone but Timmy Turner has grown up.