In this episode, Ray and Debra go to Hillcrest High School's reunion. A few months later, an episode of The Nanny called The Reunion Show (1998) would air where Fran goes to her Hillcrest High School reunion, where Ray makes an appearance. Neither shows are spin-offs of one another, but show us that both characters exist in the same fictional universe. Also, Ray Romano and Fran Drescher went to school together in real life.
During Ray's reunion, several of his classmates remember Robert. Robert was 4 years older and would have graduated before any of these students were in high school. Plus Raymond was left behind one year.