Episode Title:Parents' Day.Episode Description:It is time for the school's annual "Parents' Day", a weekend of competition with teams of a kid and their parents. Arnold feels odd about bringing his grandparents, as they are his parents, who he has not seen since he was a baby. After Big Bob calls Arnold an "orphan boy", Arnold asks Grandpa Phil what really happened with his parents, and he finds out that they disappeared after they left the country on a plane, delivering medicine, although they might still be alive. Arnold continues on with Parent's Day, with Phil and Gertie. He realizes even though they are not his parents, they raised him and made him who he is, which is what parents do.