How is Freddy Kruger even a character? His back story isn't even revealed for several films. Basically in the first film he's just a big, slimy McGuffin that people run from.
Sid the sloth, on the other hand, has plenty of character background.
Sid: My family abandoned me. They kinda migrated without me. You should have seen what they did last year. I mean, they got up early, and quickly tied up my hands and feet, and gagged me with a field mouse, and barricaded the cave door, and covered their tracks, and went through water so I'd lose their scent, and... and... who needs them anyway?