Do We Have This One?

I can't come up with an interesting way to start this out, so I'll make it simple: Something that appears in the pilot episode of a series that seems to hold weight or importance is never seen again for the rest of the series. This might be due to the fact that the concept introduced in the pilot was from an earlier draft or that it didn't fit the style of the story, but they are still there.

Other quirks include an actor being replaced or a role being changed around. Sometimes these changes are dealt with or mentioned in a later episode, but often they are simply forgotten.

Examples

Live Action TV:

• If the Mash movie were to be considered a Pilot to the television show, then the replacement of the majority of the actors for the TV show counts for this trope.

Western Animation:

• In the Sonic SATAM series, the pilot had the enemy "Buzz Bomber", an enemy from the actual Sonic game, menace the heroes in swarms. After the first episode, they are never seen again.
  • Princess Sally also gets a severe design change after the pilot with no real explanation.
• The titular heroine of Cybersix is seen consuming some liquid from a vial found from one of the mooks she just defeated in the first episode. She is never shown doing this again, although it is mentioned in the series finale.