Greg receives bad grades in school, is addicted to video games, especially the fictional Twisted Wizard, and loves junk food.

[19] Kinney has also denied the sociopath theories stating he always saw Greg as an "accurate kid" and people who give him that distinction are "missing the joke".

[11] After the film series was given a reboot during the acquisition of 21st Century Fox, Greg was voiced by Brady Noon in the animated adaptation of the first book and its sequel.

[26] Tidy Books wrote that Greg never learned from his lessons and rarely gets punished or gives sincere apologies, and that the writing is too subtle for kids to realize that he is doing the wrong thing and is an unreliable narrator.

[27] Some, such as reviewer Declan Rowles, have criticized the disapproval against the character, stating that the series doesn't glorify Greg's behavior and the majority of children understand that.

Hall argued that Greg's self-delusion and hubris, such as his attempts to belittle Rowley Jefferson or his misguided pursuit of popularity, is central to the series' humor.

He compares Greg's struggles with contemporary issues, like technology clashes and commercialism, to literary figures like Adrian Mole and Gordon Comstock, portraying him as a voice of modern frustrations.