I don't know how many people have this mindset, but I think a lot of people will agree with this.
Kerplunk is where Green Day really started to sound like Green Day. I mean, Dookie for me is really Kerplunk, but not quite as good (No hate on Dookie, I just like Kerplunk more). Insomniac is the same thing, but much darker. And Nimrod is like they combined it with Warning. 39/Smooth is in its own category.
The guitar work and bass work is a lot like what we hear on Dookie: fucking amazing. It's a very faced paced album, like Dookie. The drumming honestly reminds me of Insomniac.
I feel like with a lot of the 90s' albums, they took a lot of influences from Kerplunk.
Kerplunk is their most significant album, in my opinion. Not only what's up there ^, but because it got them so popular. And it deserves more recognition for being so fucking amazing.