Readalikes...Wimpy Kid

Diary of a Wimpy Kid is incredibly popular at my school. Yesterday, a student who has read them all asked if there were other any books like them. Any suggestions?

I'm interested in the answer too as both my boys (8 and 13) have read and loved all of them and I don't know of any other that are really like them.
My boys have both read and enjoyed a few Andrew Clements - Frindle, Lunch money. They're realistic fiction and I think aimed at the same kind of age group as the Wimpy Kid books but other than that they're not like them.

I think one of the reasons that it's so popular is because it's so unique! That being said, I have a few suggestions that might be of interest, depending on the age of your student:
Herbert's Wormhole, anything from the Stone Rabbit series, anything from the Regarding the series.

These books are skewed a little younger than the Diary of a Wimpy Kid series, but I've found that the Diary books are attracting a younger and younger crowd. Good luck!

Here's what I recommend at the bookstore when I'm working and people ask for Wimpy Kid-esque books. They are either wanting humor and/or graphic novels, usually.

Kit Feeny is a beginning reader graphic novel series that is very funny.

Also Donuthead by Sue Stauffacher is funny.

The Day My Butt Went Psycho is supposed to be really funny too, although I haven't read it.

Genius of Unspeakable Evil and I want to be your Class President for middle schoolers and up. Hilarious!

I always recommend the Bone series by Jeff Smith to kids who like Wimpy Kid. Since Wimpy Kid is sort of graphic novel-y, other graphic novels tend to go over well with fans. And Bone is awesome even if you're an adult.