Yes. Why? Why not.
SEGA® is a registered trademark of Sega Sammy Corporation. Mega CD™ is a trademark of Sega Corporation. I do not own any rights to SEGA® or Mega CD™. However, this should fall under fair use as this is on Scratch, a platform that does not make money. I have made up my own company (X Communications) for this project. You can use it wherever you want, I do not own any entity.