Do We Have This One? Needs A Better Description. Rolling Updates.

Bar graphs. Line graphs. Pie charts. Pictographs. They're typically found on the statistics page of your newspaper, and probably unnoteworthy... so one might not expect them to be used for humor.

There's an odd appeal, though, in graphing things that generally aren't expected to be graphed. Hence, the Graph Joke. Most common in webcomics because of their target audience.

This can apply to tropes, too. For example, a line graph can show a positive correlation between power and glowiness of weapons, and a pie graph illustrating the occupations of murderers can have a rather large "Butler" slice.

Examples

Live Action TV

• David Letterman's "Charts and Graphs" desk bit is all this. Example.
• How I Met Your Mother has the Hot/Crazy Scale, which shows how women rate according to how hot versus how crazy they were. Another episode had Marshall going overboard with making charts, including a pie chart on bars and a bar chart on pies.

Stand-Up Comedy

• Dmitri Martin's stand-up comedy routine often features several graph jokes, presented hand-drawn.

Web Comics

• Saturday Morning Breakfast Cereal is well-known for using this kind of joke. If I listed them all it'd easily double the page length, but to say that he more or less coined the term "graph joke" should be enough.
• XKCD, being as mathematics-heavy as it is, dabbles in this on occasion as well; for example, the famous comic about Cuteness Proximity.
• Cyanide And Happiness once graphed the phenomenon of the Graph Joke. And don't anybody dare say "Graphception".
• El Goonish Shive uses this one a few times, lampshading it once by Eliot wondering where his parents suddenly got the graph in question to display.

Web Original

• GraphJam is a website dedicated wholly to this trope.
• On TV Tropes itself, the page image for Schizophrenic Difficulty.