Adventures of Sonic the Hedgehog/WMG

Tails is really Royalty
In part two of the Quest for The Chaos Emeralds saga, Merlin tells Robotnik that in order to use the emerald he must become King. Tails, however, was able to activate it and gain a Heroic Build without getting the crown. The reason? The King's daughter married a vulpine nobleman, with Gender Equals Breed being in effect, making Tails a decendent of Adventures of Sonic the Hedgehog's King Arthur. His past before meeting Sonic was never fully explored, so it's possible that he's the long lost heir to the throne.
 * That could also explain how the 5 Sonics and Tailses defeated the Supreme High Robotnik despite having that Emerald in his possession.

This series is canon to the games
The show takes place between Sonic 4 and Sonic Unleashed. And going by the above...
 * Tails' personality in the games appears to be largely based on a less extreme version of his personality here - Exactly what could be expected from growing a few years.

The series takes place after Sonic the Hedgehog
Where the Freedom Fighters have disbanded, and Dr. Robotnik never fully recovered from his Villainous Breakdown at the end of the last episode.

They aren't really speaking English
See this scene from Tails's Tale. Look at the obvoiusly non-English writing on the monitor.