People keep going on about sitcoms pushing boundaries and breaking taboos, but I think there are still plenty of taboos that have not really been covered in sitcoms yet.
For example, we've had plenty of gay and lesbian characters in sitcoms, but not that many who are transgender (possible example: Barbara from The League of Gentlemen) or fetishists (possible examples: Rodney from Only Fools and Horses and Dominic de Sade in Operation Good Guys).
Can anyone else think of characters who break these taboos, as well as other taboos not covered much by sitcom?