The "Sayonara Zetsubou Sensei" Primer
Anime
Goku? Zan? A straight-forward list of the series that comprise the "Sayonara Zetsubou Sensei" anime saga.

Special, 2008,
1 ep
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Author:7
A summary special introducing the female characters.

Special, 2008,
1 ep
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A summary special introducing the female characters not yet introduced in the first special.

TV, 2009,
13 eps
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Author:9
Third TV anime series, and fourth part of the main anime overall.

OVA, 2009,
2 eps
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Fifth part of the main anime. (An OVA)

Special, 2012,
1 ep
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Author:-
A special included as a bonus to those who purchased all three Blu-ray box sets.

Special, 2012,
1 ep
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Author:-
A special short included with the Blu-ray box sets.