Epithelial cells, like those on the wings of a fly, are polarized, with an asymmetric distribution of molecules and structures inside a cell. In Planar Cell Polarity (PCP), all epithelial cells in a particular region get collectively polarized and aligned along the proximal-distal axis. PCP is an example of cellular phase transition through local and global interactions. We use a lattice-based spin model to capture the essential aspects of this phase transition. In this model, the alignment of cells leads to clusters of aligned cells, and such clustering exhibits a percolation transition. We show that percolation transition is crucial to achieve robust collective alignment of cells even when some cells have aberrations. In this talk, I will discuss various behaviors of this toy model. I will illustrate that if we remove the bells and whistles, a 'complicated' biological phenomenon can be equated with a 'simple' physical model that captures the behaviors of many other phenomena.