Little problem with xscale and tikzducks
The book is a node , and nodes are only transformed (rotated etc) if you use the transform shape key. But naturally this will also mirror the text, so you need reflectbox to get it back::
\documentclass{article}
\usepackage{tikzducks}
\setlength\parindent{0pt}
\begin{document}
Initial image:
\begin{tikzpicture}
\duck[book=\scalebox{0.5}{\TeX}]
\end{tikzpicture}
Image with \verb|xscale=-1| option:
\begin{tikzpicture}[xscale=-1,transform shape]
\duck[book=\scalebox{0.5}{\TeX}]
\end{tikzpicture}
\begin{tikzpicture}[xscale=-1,transform shape]
\duck[book=\scalebox{0.5}{\reflectbox{\TeX}}]
\end{tikzpicture}
\end{document}
This problem has been fixed in version 0.6 of the tikzducks
\documentclass{article}
\usepackage{tikzducks}
\setlength\parindent{0pt}
\begin{document}
Initial image:
\begin{tikzpicture}
\duck[book=\scalebox{0.5}{\TeX}]
\end{tikzpicture}
\begin{tikzpicture}[xscale=-1]
\duck[book=\scalebox{0.5}{\TeX}]
\end{tikzpicture}
\end{document}
now gives