If you purchase the Sonic the Hedgehog movies on Blu-ray, you have the legal right (in many jurisdictions, under "Fair Use" or format-shifting provisions) to create a digital backup of that disc for personal use.
The search for Sonic content in MKV format is driven largely by fans looking for the "Definitive Edition" of the films or series. Here is why MKV is the gold standard for Sonic enthusiasts: sonic the hedgehog mkv
Disclaimer: This article is for educational purposes regarding file formats and digital media. Piracy is illegal and harms the creators who bring these characters to life. If you purchase the Sonic the Hedgehog movies