What is the meaning of Brook's 45 degrees technique? As seen in the anime/manga Brook performs a technique called 45 degrees which seems to be funny somehow. 
It's this some kind of Japanese joke or pun?
Apparently the move is a reference to Micheal Jackson.  His dancing style has, at times, included moves where he angles himself further than most people can using his feet as support.

Alot from the Thiller Bark arc references Micheal Jacksons Thiller music video.

Going beyond 45 degrees makes it difficult, if not impossible, not to fall over which is frequently mentioned.

When he needs to get stronger, he seems to think leaning more will somehow make him more useful.

The leaning against a wall makes the move much less impressive but, hey, that makes it sillier.