Certification
- Australia:M (some episodes)
- Australia:MA15+ (some episodes)
- Canada:R (Manitoba, most volumes)
- Canada:AA (Ontario, most volumes, VHS/DVD rating)
- Canada:13+ (Quebec)
- Canada:16+ (Quebec, some volumes)
- Germany:16
- Hungary:18
- Netherlands:12
- New Zealand:R16 (some episodes)
- New Zealand:R18 (some episodes)
- Sweden:18+
- United Kingdom:PG (seasons 1-4)
- United Kingdom:15 (some episodes)
- United Kingdom:18 (some episodes)
- United States:TV-14
- United States:TV-MA (DLSV, DVD rating)
- United States:TV-MA (DLSV, cable rating)
- United States:TV-MA (DLSV, some airings)
- United States:Not Rated (original rating)
- United States:TV-PG (seasons 1-4)