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.
What Kind of Pokémon are You?, a song performed by a man representing Dexter, Ash's PokéDex.
Psyduck's cameos, which are used to change sets.
Crowning Music of Awesome: You Just Can't Win for all the fans who would've liked to see Ash and Giovanni actually face each other. This was the closest they'd come to a fight until the Best Wishes series 13 years later. The song is made even cooler in context, as it takes place after MechaMew2 defeats Pikachu, so Ash tries to fight Giovanni himself.
Team Rocket's Rockin' (Double Trouble) is pretty damn awesome. As is Giovanni's Villain Song.
Evil Is Cool: Giovanni, Team Rocket, and even the Rocket Grunts completely steal the show.