Spongebob is somewhat well-known in Japan IIRC.The "Jojothan's" on p.12 is such a cheeky way of avoiding copyright while also making a convoluted reference to the source of Jonathan's name.
Between this, and stuff like the Spongebob face or the rage comic face from earlier chapters, I always suspect that the mangaka has some kind of intimate familiarity of American culture.