Basic Trope: A character is introduced whose significance to the plot doesn't become apparent until later.
Our hero meets Beth, who makes small talk about taking her small-jet pilot certification. When the villain escapes at the airfield in his jet, our hero flags her down on the runway and they follow the villain.
Joe shows up in a few episodes as the hero's friend's roommate. Turns out he's been working for the Big Bad all along.
Beth is an pilot-certified, chemistry major who counterfeits money and engages in con games in her spare time. She owns an antique sword and has the C.E.O. of Heroic Industries as an uncle. Everything in the story is solved by her many coincidental talents and possessions
Beth isn't introduced until after she takes down the villain's plane.
Joe is introduced as a villain, but after he's defeated he keeps up a minor role as the hero's friend's roommate.
The hero meets Beth and keeps her in mind in case he needs a ride. The villain escapes in a submarine.
The hero finds notes around his friend's apartment, in the roommate's handwriting, which allude to villainy, but it turns out that this was planted by the villain, and Joe really is unimportant.
The hero meets Beth and keeps her in mind, the villain escapes in a submarine, but Beth knows enough to pilot a military jet armed with depth charges.
At least, that's what Joe wants the hero to think...
Parodied: Beth talks about her ability to light on fire any person with a name starting with a vowel. The villain's plane burst into flames the moment she is reminded his middle name is "Owen"
Zig Zagged: Beth mentions early on in the story that she's learning to fly, but when the hero asks her to pilot an airplane in pursuit, she explains that she's only licensed for helicopters. However, she does have a friend visiting from Brazil who's qualified to fly the plane, and since Beth happens to be fluent in Portuguese, she is able to translate for the hero. Later on, at the villain's base, it turns out that the villain is in possession of a number of heavily armed military-grade helicopters, but Beth discovers that the villain designed and manufactured the helicopters himself, deliberately making the controls so that anyone not trained specifically for his model of helicopter would be unable to fly it. However, given her previous experience with helicopters, she comes up with a method that would disable the helicopters without being immediately apparent that they'd been sabotaged, so that when the villain finally discovers that his helicopters no longer work, it will be too late to fix things.
Averted: Beth's usefulness as a pilot is a major part of the plot from the beginning, as the villain's plan involves a military prototype jet.
Enforced: The Air Force sponsors the show and Executive Meddling forced Beth to be written in as crucial to the plot at a critical moment of heroism.
Lampshaded: The villain has retreated to his airship hideout; "Hey, didn't we just meet a pilot a few days ago? What a coincidence!"
Invoked: Beth, working with the villain, makes sure to "accidentally" meet the hero a few days before the villain escapes by plane, so that she can trap the hero when he goes to her for help.
Defied: The hero remembers that Beth mentioned her small-jet certification, but decides not to ask her to pilot a plane in pursuit—he is unsure whether Beth can be trusted, or he is simply unwilling to put a civilian in danger by involving them in his struggle.
Discussed: "When you're dealing with a guy who has an airship, it's smart to keep around someone who knows how to fly".
Conversed: "I'll bet Beth's piloting skills come in handy later".
Because no one expected to need a pilot, Beth wasn't brought along on the mission.
After realizing that someone as unimportant-seeming as Joe had turned out to be such a formidable enemy, Bob becomes paranoid and suspicious around everyone whom he doesn't know well.
Reconstructed: Beth may not be a good pilot, but she can get her instructor to fly them both.