Sasquatch and Rocking

Captain Ed tries dissuading Tenacious D from following through on their dream, calling it a myth like Sasquatch. It is not until Jack and Kyle reach the "Acceptance" stage of their dream's death do they see Sasquatch for real, the two of them immediately breaking out into a song as their dream had spontaneously come back to life.

Example of:
If Jesus, Then Aliens