These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
"Aaron 1," the song that plays during the montage of the war in the film's prologue. It has since returned for intense action sequences in the series, such as the Nando VS. Zoey battle of the Sinnoh Grand Festival.
Aura does come up occasionally in the series from the DP arc, most notably when Ash uses it to save a kidnapped Riolu. It's more a case of Refusal of the Call that actually sticks - Ash instead chooses to continue following his goal as a Pokémon Trainer.