Setting Identity to on or off in SQL server

To insert explicit values into the identity column , do the following :

SET IDENTITY_INSERT Tbl_Cartoons  ON
GO

-- code to insert explicit ID values

SET IDENTITY_INSERT Tbl_Cartoons  OFF
GO

You actually want to use SET IDENTITY_INSERT Tbl_Cartoons ON before attempting to insert explicit values.

You're saying that "I am going to be responsible for inserting values into the IDENTITY column".

SET IDENTITY_INSERT Tbl_Cartoons OFF says "I'll let the system take responsibility for inserting values into the IDENTITY column".