Romana → Serials → TARDIS → Doctors → Characters with one name → Character names → Honourifics → Magazine issues → Years → Eras → Human → Parts of a series without clear individual titles → Humanoid → The Monk → Dates → Astronomical objects → Lists of appearances → The Master → Universe → K9/Background → Integers → Fandom names → Speedy renames → K9
Though the issue of an extra hyphen is trivial in most instances, on a wiki it does actually matter whether it's present. Users will be less able to find articles and categories about K9 if we don't impose strict guidelines about the spelling. Thus, it's very important to use the unhyphenated K9 in page titles about the character and television series, and you should always use that spelling for category titles, so that other users can reliably find all pages and categories about K9 using the auto-suggest feature.
Roman numerals after K9 — K9 Mark I — K9 Mark IV — indicate a model which was primarily used in a BBC production. The model used in the Australian K9 television series is to be called K9 Mark 2 to differentiate from Romana II's pet, K9 Mark II.
There are a couple of instances in which it's okay to use K-9 instead of K9.
If the title of a work actually includes the hyphen, like the comic strip K-9's Finest Hour, then it should remain in the title.
Furthermore, if you're quoting from a printed source where the K-9 variant is used, you should use the hyphen to better reflect that source. In some cases, such as a few cast lists in the BBC Wales era, K-9 is used, so you must use the hyphen to comply with T:CAST.
For these reasons, hyphenated redirects, like K-9 Mark II, shall be maintained for all of the "Roman numeral K9s".