جَاءَ هَؤُلَاءِ. — Hāʾulāʾi is built on kasra, in nominative position as fāʿil.
رَأَيْتُ هَؤُلَاءِ. — Built on kasra, in accusative position as object.
مَرَرْتُ بِهَؤُلَاءِ. — Built on kasra, in genitive position.
Summary: one fixed form can occupy three different case positions.