"Hello, Mrs. Cumberdale" boy

The "Hello, Mrs. Cumberdale" boy is one of Bart's "friends and well-wishers" that he invited to his pool.

History
After Marge asked Bart if all of the kids in the house were friends of him, four teens said hello to a kid who is not Bart, and this last boy said to Marge: "Hello, Mrs. Cumberdale".