Timmy distracts Cosmo to add his own rules to the Da Rules book. One of the rules he writes, is that a godchild can use his/her fairy for love-related themes. He wishes for a crowd of Trixies who love him for who he is.
Trixie is seen during the song "Adults Ruin Everything" as one of the protesting kids. Notably this is the only time she appears alongside fan-rival Tootie. She is also seen delivering a pizza to Timmy after he becomes President. She is seen getting on the bus in, Unfundamentals. Later she is seen roller-skating, in the reprise Mix.
Timmy uses You Doo Dolls to clear Veronica, Tad, and Chad away from Trixie's lunch table so he can be alone with her. After getting to know him, Trixie is momentarily impressed, but Tootie unknowingly uses another You Doo Doll to make Timmy say she is prettier than Trixie, who dumps her lunch on Timmy's head and storms off.
Trixie is seen on a swing when Timmy attempts to get a kiss with her while wearing a love amulet given to him by Mark Chang. The amulet turns out to be a lie (part L of F.L.A.R.G.) and Trixie quickly screams for security to throw Timmy away. Trixie is later seen holding hands with Timmy in a photograph montage with other pleasant events that Timmy cannot remember due to amnesia (part A of F.L.A.R.G.).
After Cosmo becomes pregnant, a montage of him throwing up on Timmy is shown, during one moment he impresses her by trying to give her a flower but the moment is ruined when Cosmo throws up on him from above.