It had a shorter run than some of the other kids' shows on this list, but Hey Arnold! became a staple for late-90's kids. The story of a boy living with his grandparents in the city boarding house they own involved everything from wacky adventures to more poignant episodes dealing with real-life issues. Although attempts to reboot or revive the series have flopped in recent years, it's still a memorable part of '90s Nickelodeon.