- Squick: The cure for Phineas and Ferb's predicament in Stuck Like Brothers: drinking the run-off from the invention that caused it in the first place.
- The Woobie: The titular duo spend a lot of time in this position in each story. Here's the exact list for who and how this position is filled in the stories.
Ferb, you're kidnapping me. Why are you kidnapping me?
- Timeloops: Phineas gets to think his brother will forget him in the future, Future Ferb blames himself for temporarily erasing his best friend from time (even more-so because he didn't know it was temporary) and Future Phineas lost track of Ferb after coming back from deletion.
- Ghosts: Phineas is lead to believe Ferb died in an explosion while Ferb slowly realizes he's invisible to the world and can't reassure Phineas.
- Stolen Identity: Ferb has his identity stolen and has to watch the impostor abuse Phineas while Phineas slowly devolves into utter terror of the person he thinks is Ferb.
- Of particular note is the scene where the impostor forces Phineas into the truck the brothers frequently drive and locks him in. When Phineas realizes what's going on, this is what he says.
- Stuck Like Brothers: Ferb slowly loses control of his body and possibly will cease to exist as a person. Phineas blames himself for this and has several bad dreams about the results of this escapade.
- Mind-Trapped: Ferb is stuck in his own head in a world where he doesn't exist nor does his father and his mother and siblings don't recognize him. Phineas blames himself for Ferb's coma and worries himself sick until Ferb awakens.
- Species Is a Constant: Ferb blames himself for turning into a dog. Then when Ferb disappears, Phineas spends the remainder of the story until he's found in an utter panic.
- Lifeleap: Phineas is terribly distressed at the possibility that he and Ferb could stop being close as they grow up; this is so bad that he tells a teenage Ferb that he isn't his (Phineas') brother, landing said teenager in this trope. Then once Phineas moves past his fear, he becomes indirectly responsible for teen Ferb breaking his leg and thought he might have caused worse for a while.
YMMV / Sols06's Phineas and Ferb Verse