If you control Miss Fortune, Buccaneer (which allows friendly units to be played to open battlefields), can you play a hidden unit (like Teemo) or a unit from a hidden spell effect (like Sprite Call) to an open battlefield instead of the battlefield where it was hidden?

Ruling: No. A hidden unit must be played to the battlefield where it was hidden, and this restriction cannot be overridden by Miss Fortune's ability.

Sequence:

• When playing a hidden unit, you must play it to the battlefield where it was hidden
• Miss Fortune's ability grants permission to play units to open battlefields
• The "must" requirement from hidden rules supersedes the "may" permission from Miss Fortune
• This applies both to hidden units themselves and to units played via hidden spell effects

Nuances:

• The restriction is based on "can't beats can" as a broad method of determination - requirements trump permissions
• Miss Fortune's ability adds to valid locations for normal units, but cannot override the mandatory restriction on where hidden units must be played
• The hidden unit has only one valid location (the battlefield it was hidden at), and this cannot be expanded by other effects
• This is not about whether hiding is valid at the new location, but about where a hidden card can be played when revealed