Thing is a member of the Addams family.
He is a disembodied green arm.
The New Scooby-Doo Movies
Gomez Addams asked the Scooby gang to shake hands with him/it.
Uncle Fester later surprised Scooby-Doo by having him open a box with Thing in it as Morticia Addams's going-away present. (Wednesday is Missing)
- In later incarnations of the Addams family (outside of Scooby-Doo), Thing is flesh coloured and just a hand.