A mug is home.
Stanley Pines never really had a ceramic mug, ot was always those plastic and carton cups for his coffee and his coffee always tasted like shit...he always liked it creamier, with milk and sugar but that costed extra and caffeine is what kills his hunger easiest.
When he began living as Stanford Pines he used the dishes that were already there, finally he could carry around a steaming cup of coffee down to the basement, boring and white.
Then he became Mr Mystery and began selling mugs as part of merchandise: a classic ugly yellow with a question mark. A mug?
It was for customers only, or at least it was supposed to be but Stanley fojnd himself taking one for himself. He found himself dropping the Stanford act more and more because yeah it was a ceramic mug but it was HIS.
Then the little twins came along...by then things had changed a lot but it was never truly home. It was Ford's house afterall. Still, if Stan closed his eyes and ignored the many nights and early sunrises he spends in the basement, he could almost pretend it was a home.
He is one day handed a mug. It is glittery and messy and probably has materials that wouldn't be safe do drink from. It is his mug, given by the twins. It is HIS.
A ceramic mug is something you only get when you settle, when you plan to stay and wake up under the same roof for a long time. It is a promise of home.
A mug is home.
Later on, when Ford and Stan prepare to sail away, Stanley insists they shoukd make their own mugs from scratch.