this not in something that you catch yourself at a random point-- this is what that's what she said is used for, just at yourself. This clause is used specifically in a response to someone who just said "that's what she said", as to keep them from saying it more than once.
unlike the common "that's what she said jokes", that's not what she said can be used when describing an act that she wouldn't do or something she wouldn't like. a reverse innuendo. because a normal audience is thrown off by this, it often results in a more uncomfortable situation.
m: we should bring back the "that's not what she said"
k: I am sure it won't be hard.
(that's not what she said)
m: Yeah, I know, but sometimes you're just not in the mood to do something that hard.
(That is not what she said)
k: This exchange could go on for ages. We need to stop.
(That is not what she said)
m: good call. it is never a good idea to stay up all night doing it.
(that is not what she said)
The opposite of "That's What She Said"; when an innocent statement is interpreted sexually - lack of sexual skill, small pecker, etc. - when in fact the statement refers to something else
Opposite of 'thats what she said'. A phrase added to the front of another, innocent sounding statement, which is used to create a funny, possibly obscene, self esteem boosting comment implying that what has just been said is the opposite of what 'she' thinks.
Chris: Jordan your an absolute cunt. You told everyone im a virgin, you give me shit for not driving a Ford Cortina and you screwed my fucking missus!! Your just a useless piece of human garbage!
Jordan: Thats not what she said!
Chris: Thats it man your the biggest prick I know, im gonna fuck you up real good!