A friend told me that there is a book named something like "Mathematical pranks" which lists tricks to mathematically fool and prank your friends like fake and false proofs that look ok and so. But I can't find the book. Do you have an idea what I'm talking about?
Although there probably is no book with that title, Linderholm's Mathematics made difficult is exactly that: a collection of pranks.
There also are interesting asides:
On page 156 called A parenthesis on the sex life of brackets you will learn about "the special liaisons which occur chiefly in France: monstrosities like $[a,b[$ in which two brackets of the same sex join horribly".
The book is out of print, but it is very easy to find links on the Internet for downloading a PDF version of it.