Check the uploader's reputation. Users like or "ModelWorks" have high trust scores. Look for comment sections with phrases like "The rigging works perfectly" or "Thanks for the Unity package."
Some GameJolt game pages have a "Community Assets" section or a link to a Discord server. Often, the developer won't host the .fbx directly on GameJolt (because it takes up storage space), but they will post a MediaFire or Google Drive link in the game description or comments. sonic.fbx download gamejolt
If you need a Sonic model for a non-commercial fan project: Check the uploader's reputation