This comic comes in two parts and is a pun on the baseball metaphor used to describe how far a date went regarding erotic actions.
Here is a translation of Ponytails comment: This would mean that Ponytail was about to go down on another girl, while this girl had her period.
Many people would find it disgusting to go down on a girl while she was menstruating, explaining Ponytails reaction to Cueball's Sounds tricky reply.
The second part, the diagram, depicts a much more complex version of the baseball metaphor, where baseball terms and jargon are used to describe the many and varied things human beings like to do in the bedroom. In order to understand the terms used, one may want to consult this picture: The "diamond" is the geometric pattern formed by the four bases - first, second, third, and home plate.
When Cueball answers Ponytail's question with "second base", Ponytail asks what that means exactly.
They fumble around with the definition in panel two where Ponytail ask is that Below the waist, but... Cueball tries to put this into the base system and suggest that this could be compared to the difficult shortstop fielding position in baseball, between 2nd and 3rd base.
This fits with the position of Hands on the pants metaphor from the picture below the comic strip.Then Ponytail begins with yet another base analogy by mentioning crossing the pitcher's mound, but then suddenly she brings two more, very different, sports into the metaphor: American football (with the 50 yard line) and bowling (with the ten-pin). Ponytail then brings up a third sport in her elaboration; her reference to getting a "red flag" could refer to different sports, as many sports use flags, some of them red.It is, however, most likely a reference to racing in motor sport as the red flag is displayed when conditions are too dangerous to continue the session.This makes sense when looking at the "translation" here below.Cueball, however, has not got a clue which he expresses when Ponytail asks him If you know what I mean.(Note that this comic came out less than a week after the Super Bowl XLIII, the final game of the Super Bowl of 2009, which was played on 2009-02-01).