The address shown on the envelope to forward the Walsh family mail is 933 Hillcrest Dr. Beverly Hills. In a later episode where Brandon helps a woman whose fiancée dumps her and then takes her back after realizing his mistake he gives her a totally different address for her fiancée to come to the house despite the family never moving.
When Dylan tries to call his parents, it is implied that they are still married. However, later in the show it is told that they have been divorced for many years and Dylan's mother lives in Hawaii.
When Dylan and Brandon are talking on the steps outside of school after Dylan stands up for Scott in the computer lab Dylan asks Brandon if he is "Scotch" or Irish based on his last name. He should have said Scottish or Irish.