Spyro and Sgt. Byrd are both voiced by Tom Kenny in Year of the Dragon. 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.
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. Like most game releases, Insomniac never had the full rights to the franchise, so when they wanted to move to Sony as a publisher, Spyro remained with Universal. The series 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, who then created Skylanders.
Follow the Leader: The original trilogy was obviously made to ride the trend of collect-a-thon platformers started by the success of Super Mario 64. Spyro stands out with his gliding mechanic, which gives him a platforming style that's far more horizontal than any other character at the time.
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 its characters' voice actors from Year of the Dragon. All of the cast were replaced in A Hero's Tail except for André Sogliuzzo (though Sparx sounds entirely different).
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 Morris in the Reignited Trilogy.
Prior to Enter the Dragonfly, there was at one point a Spyro game in the works for the Xbox.
Two separate spinoff games based off Agent 9 were in development. The first, Prime 8, was loosely based on the original character while the second game, Agent 9, was more true-to-text.
What Could Have Been: Whilst the fast development of the original Spyro trilogy kept there from being too many ideas that couldn't be used, there are a few notable examples:
The Spyro the Dragon 1998 Press Kit reveals there were originally plans for two more Dragon factions in the first game; Machinists and Aquifiers. Beta builds of the game had the last homeworld called "Machinists" before it was revamped as "Gnasty's World" in the final game.
It has been confirmed that there were plans for a water world in Spyro 1, features of which included a family of Amish-looking dolphin riders and an evil sea dragon boss. The boss level was recycled, sans boss, as the Aquaria Towers level in Spyro 2.
Elora was originally supposed to be a centaur rather than a faun, but the idea was scrapped because the polygon limit of the original Playstation meant that giving her four legs (which would make her harder to animate, to boot) would mean less detail on her facial features.
Moneybags the Bear was originally planned to be a Rhinoc.
Sheila underwent several revisions to try and spruce up her character model to make her more interesting, including gaining devil horns, boxing gloves, a red shirt, and even hair — yes, her Reignited redesign is actually Older Than They Think. In the end, it was decided to revert her back to her original "simple" model, because none of the additions seemed to work.
Agent 9 was originally planned to be a pig, not a monkey.
The Crystal Islands world from Spyro 3 was originally planned to be themed as a crystalized forest, with enemies made up of mutated forest creatures, such as a crystal bear and a flying beaver
a Spyro game in the works for the Xbox.