They didn't make any attempt to litigate it, because, as I understand it, a lawyer told them it was not a good idea (http://www.penny-arcade.com/2003/04/21):
We are, of course, talking to our lawyer about all this stuff. Readers have referred us to many sources in an effort to clarify our position legally, sites like Chilling Effects act as clearing houses for data useful in situations such as this. Also, interesting cases have been brought to our attention - for example, Aqua’s song “Barbie Girl” was contested by Mattel, and Aqua still came out on top (as it were). In darker news, Matt from MacHall send this interesting bit - check page 3, “Dr. Seuss Enterprises Vs. Penguin Books.” To my mind, that precedent doesn’t mean anything good for us.
I clicked on this, forgot about it and looked at the tab a while later. I only realized I was looking at old comics after a couple of fairly confusing minutes, wondering about the odd art style and why on Earth they were back to playing Phantasy Star Online, but effortlessly integrating the "fact" that there's a new EverQuest expansion coming out that is similar to the previous ones. I guess that one is a timeless fact.
