>>108714518Non-brainlet answer coming through.
First, Tootie was a fan popular character, but aside from Butch some of the other writers didn't seem to care for her. Kikeivan in particular wrote her very unflattering and was trying to tip the scales in Trixie's favor in the post-Poof episodes when he was head writer.
And even with Butch, he didn't seem to grasp her potential and literally and unironically at one point forgot she and Vicky were even sisters.
Two, Tootie was added (or at least named so) as a reference to Butch Hartman's youngest daughter. Essentially a gag role that took off like Dark Laser did. The reason she became fan popular is because the other options for shipping Timmy with (Vicky, Trixie) were either repulsive or unlikable to the point where it made Tootie the best "fine whatever" option for people who didn't want those other thots to earn something unjustly.
Basically, the Butch Man and his staff never recognized her potential, or pushed back against any attempts at such, and even the executives overlooked her and her "get a fairy" plot in favor of Chloe, who had normies screaming in the comments section of every YouTube video she was featured in "WHY DIDN'T THEY JUST HAVE TIMMY SHARE WITH TOOTIE!?". Would it have improved the show? Probably, I mean, even Chloe had some interesting plots in her season despite sharing little chemistry with Timmy.
Also, anyone bringing up Birthday Wish as a canon answer is retarded, it was written by Cynthia True during the period where Hartman wasn't even working on the show. It was a good episide mind you, but it doesn't explain the plothole anymore than Fairy Idol explains a similar plothole with Chester.
