A while back I was trying to paste a figures into a LaTeX document this evening with names like
foo_32.2.png, putting a parameter value into the name of the plot. The former worked but the latter didn’t.
It turns out the
\includegraphics command parses the file extension in a naive way to determine the file type. When it sees
foo_27.png, it says “OK, a
.png file”. But when it sees
foo_32.2.png, it says “
.2.png? I’ve never heard of that file type.”