Slumber Party Pals

The Slumber Party Pals are a fictional series of books that appears in Diary of a Wimpy Kid: Hard Luck.

There are about 100 volumes and Greg has read them all, stating that even though they are meant for girls, they are addictive, and once you read one, you have to read them all. Greg discovered the series during silent reading. The first thirty editions were good, but Greg believes the later ones weren't so good, as the author started to run out of ideas.

According to Greg, in each volume of Slumber Party Pals, the plot is pretty much the same - the two main characters (Lindsey and an unnamed second girl), always get into fights over something small, then by the end, they cool down and make friends again.

Greg states reading the Slumber Party Pals series is how he knows all about how friendship works with girls.

Characters

 * Lindsey - one of the main characters that always gets into fights with her friend.
 * Unnamed girl - Lindsey's friend. The two always fight.
 * Justin - a competition boy that the unnamed girl and Lindsey both have a crush on.

Known Volumes
There are about 100 volumes of Slumber Party Pals. These are the known editions:
 * #3 - Teamwork! - Appears to be about the two girls babysitting or looking after a newborn baby.
 * #7 - Boyfriend Trouble - The girls presumably fight over a boyfriend, and Lindsey appears to lose.
 * #9 - 'Best Frenemies - The girls presumably fall out as usual.
 * #87 - Lindsey Loses a Mitten - Lindsey probably loses her best mittens and probably accuses her friend of stealing them, leading to another fallout.
 * Unknown Volume - The girls fight over purple lip gloss and the unnamed girl accuses Lindsey of stealing it, with Lindsey replying that she only wanted to use it to kiss Justin at the roller rink. The fight is resolved with Lindsey apologising for using the lip gloss, and her friend apologising for kissing Justin, to Lindsey's surprise.