Bad Export for You: The Japanese release of the first two games was plagued by numerous issues, including numerous glitches, a nearly uncontrollable camera, and most inexplicably, signs scattered literally everywhere that caused "helpful" tips to pop up whenever they were hit with Spyro's flame, accidentally or otherwise. Understandably, the first two games did not do well in Japan, and as a result Year of the Dragon never made it there.
Channel Hop: Went from Universal Interactive for the first few games, then to Vivendi Universal (the name they assumed before the NBC merger, after having merged with a French conglomerate), who then organized Spyro under video game stalwart Sierra, who they had bought a few years before. And after that (after most of Universal had become part of GE, then Comcast), the remains of VU/Sierra went to Activision.
Executive Meddling: Heck, this whole franchise was built around this trope. Originally, Sony of America wanted to create a "kid friendly game and character for the PlayStation" (considering the games at the time were... ratheradultandteen oriented), hence the creation of the franchise, in which Insomniac never even had the full rights of in the first place, which resulted after Year of the Dragon's release that the franchise was sold and then became a Franchise Zombie until purchased by Sierra, who being way past their time ended up being bought out by Activision along with the rest of the Universal/Vivendi group.
Hey, It's That Sound!: For whatever reason, the sound heard when you light a tiki statue in Season of Flame's Tiki Torches world is the sound used in the Crash Bandicoot games when Aku Aku is equipped.
All of the Spyro titles featured at least one cast change, with the exception of Enter The Dragonfly which kept all of it's characters' voice actors from Year of the Dragon. All of the cast were replaced in A Hero's Tail except for Andre Soqliuzzo (though he voices Sparx completely differently anyway).
Elora and Handel's actress has changed every time the two have appeared in the same game: Melissa Disney in Ripto's Rage!, Carolyn Lawrence in Year of the Dragon and Cassandra Lee in the Reignited Trilogy.
Spyro and Sgt. Byrd have been voiced by the same actor in both games Bryd's been voiced in: Tom Kenny in Year of the Dragon and Jess Harnell in A Hero's Tail. Considering Spyro has to interact with Byrd to start the latter's stages, a good part of Byrd's dialogue is spent talking to Spyro.