You can find a really funny comic strip about PhD problems and grad student’s life in the Piled Higher and Deeper website (www.phdcomics.com). It’s great to realize you are not the only one person in the world having problems with your research 
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There are lots of comics strips already published, but most popular ones are linked in the main page. Check for example Grad Motivation Graphs, Grad Student Etiquette or Conference in Hawaii (newer ones are coloured and better drawn, but anyway they are funny).
Hope you enjoy them.
