This talk will focus on four families of symmetric functions: Schur functions, stable Grothendieck polynomials, k-Schur functions, and affine stable Grothendieck polynomials. These families represent the (intersection cohomology/K-theory) classes of the (Grassmannian/affine Grassmannian). In every case, tableaux combinatorics describe the change of basis matrix between these functions and the complete homogeneous symmetric functions, and these combinatorics correspond to a geometric Pieri rule. In joint work with Jennifer Morse, we have been studying what happens when we replace the homogeneous symmetric functions with their 't-analog'; the Hall-Littlewood functions. I will present an (as yet, incomplete) combinatorial approach to understanding this generalization.