Phew!
Ok, for those of you who are not as familiar with the English language as Mr. Scott Adams, here's the link you need to check out - http://www.urbandictionary.com/define.php?term=circlejerk
Check the meaning in #3 which is what is applicable here.
Brilliant! This is one of the closest Scott has come to crossing the line. A really good laugh!! And is Alice's face speaking or is she portraying a blow-up doll? Hmm, the power of suggestion....