It's a pie chart that looks like Pac-man. it's not exactly a pun so much as 'pac-man looks like a pie chart, but if you look at it literally, the area of a pie-chart that looks like pac-man.. looks like pac-man"
Seems more like it's Shaped Like Itself than a Visual Pun.
Not right away, not right away
There's a trope which I would add, but I don't know the name. I presume it must have one.
Namely, that there has for years been mystery and even controversy regarding the identity of the (round, light green) fruit which follows the apple. It's variously been called a grape, a bunch of grapes, a pineapple, or even a grenade (I think those who reckon either of the last two must have weird imaginations). But the mystery has been cleared up by the release of Pac-Man Ball, which has pictures of various Pac-Fruits complete with captions giving their names; it turns out that the mystery fruit is a melon (intact, rather than sliced open as is usual for arcade melons).
Just to justify my monsters/ghosts and energizers/power pills/power pellets edit....
The original instruction art from Pac-Man (which calls them "Energizers" and "Monsters"): arcarc.xmission.com/Scans/Bezels/pacman_BEZEL.jpg (biiiig image)
The same, from Ms. Pac-Man: www.arcade-museum.com/images/104/1048803048.jpg
Atari 2600 instruction manual (which calls them "Power Pills" and "Ghosts"): http://www.atariage.com/manual_html_page.html?SoftwareLabelID=342
Edited by DarkStorm