Recently I wrote about an interesting fan theory for Ed, Edd, n Eddy and it creeped a lot of people out, including myself. It's fun to take a look back at classic shows with the benefit of hindsight, and to realize that there may have been a deeper, often darker backstory to some of those seemingly innocent characters.
I came across another one for another one of my favorite shows growing up, The Fairly Odd Parents. The theory comes from a Reddit user named Super_Inuit. Obviously, the show already had some hidden meaning and you could very easily extrapolate on these magical secondary parents for Timmy. Were they hallucinations? How did they come about? When did they come? Etc.
Well, an interesting theory (that you should take with a grain of salt, because it's really just a fun way to look at a kid's show) states that Cosmo and Wanda are actually anti-depressants, helping him cope and making his problems a little bit less exaggerated. There's nothing wrong with taking anti-depressants, and many people do. Many people have these Fairly Odd Parents of some sort that help them get through the struggles of life.
In Timmy's case, there is a lot of evidence. There was an episode in the show that said the fairy godparents were only going to be around when Timmy needed them. Like pills, they could alleviate his stress and anxiety and help him out, so to speak.
There's an episode where he uses a hand-held aging machine to see if they'd still be with him into his twenties. They sure were! He may at some point become dependent upon them, like many humans do.
In the pilot episode Cosmo and Wanda appear to Timmy on the night that Vicky comes into his life, basically saying that they start when the problems do. The idea, perhaps, is that Cosmo is Zoloft and Wanda is Prozac (Zoloft is said to make you giddy, while Prozac makes you more analytical). They bring lighter moods to Timmy and let him be his best self.
Also, keep in mind that problems often arise when he abuses the magic, much like how problems can arise for people with prescriptions to these pills if they take too much. Some of the other fairies could also be recreational drugs that aren't as helpful as the "parents" he was actually prescribed to in Cosmo and Wanda.
Take a look at the intro to the show. Timmy is clearly in a bad mood when he gets off of the bus, but everything brightens up once he gets into his room with Cosmo and Wanda...
Legit theory or trying too hard?