This answer mentioned that the size of a node usually depends on the size of the content. For instance in following example the circle will have size 2cm
as long as the content doesn't force it to make it bigger. Is it possible then to set the size of this circle to a fixed value that is independent of the size of the content? (So a too large content might possibly overflow.)
\begin{tikzpicture}
\draw node[fill,circle,minimum size=2cm] {content};
\end{tikzpicture}
fill=yellow
... BTW, nice trick for the answer!