Recap: Phineas And Ferb Rollercoater The Musical
"You know, Ferb. One of the best times we ever had was when we built that rollercoaster. We should do it again, but this time, as a musical!"
On a day very similar to the very first episode, the not-quite-as-snarky-anymore Phineas remarks that one of the best times they ever had was when they built that rollercoaster, so he decides to do it again, as a musical!