Jeff Kinney stopped by CBS News Boston to discuss Partypooper, the 20th installment in his popular Diary of a Wimpy Kid series of children’s books.

Kinney’s book, published Tuesday by Amulet/Abrams, follows the titular wimpy kid, Greg Heffley, whose parents forget his birthday and organize a do-over party afterwards. A critic for Kirkus called the book “a festive frolic—even if the frosting on the birthday cake does turn out to be mayonnaise.”

Kinney told CBS News Boston co-anchor Chris Tanaka, “[Greg’s] parents actually forget his birthday, which I think would be every kid’s worst nightmare. I think this one might actually cause a little bit of trauma in kids, wishing and hoping their parents don’t forget their birthdays.”

Tanaka asked Kinney about the progression of Greg over the past 20 books.

“The thing about cartoon characters is that they can’t really change,” Kinney said. “They’re something that’s reliable, like Charlie Brown always has to miss the football. He can’t really develop, because cartoon characters are like a security blanket to kids and to their adult fandom, so I think that they need to be reliably same.”

Tanaka asked Kinney if he ever laughs at his characters and their antics.

“Some writers say that they sort of believe in their characters, or their characters talk to them, and I’ve always found that to be a little bit pretentious,” Kinney said. “But now, after all these movies, books, and even a musical, I’ve started to believe in the characters. They seem really separate from me. I do get a laugh out of the characters.”

Michael Schaub is a contributing writer.