Most of the characters get 'pink eye'. This is represented by them getting a pink aura around one of their eyes. In fact, pink eye, or conjunctivitis, most often only colors the white of the eye pink.
When Leonard and Sheldon are waiting for Georgie, Sheldon complains about a standee of him using a stethoscope on a tire, asking what he'd even be using one for. Leonard placates him by stating that he could be listening for air leaks. However, it is a stack of 6 tires, which wouldn't be mounted on rims and therefore have no air in them to listen for. Both are geniuses, Sheldon is highly observant, and Leonard drives, at least one of them would have realized this.
Maybe Leonard thought the stethoscope would be used after a tire is placed on a rim and filled with air.
Maybe Leonard thought the stethoscope would be used after a tire is placed on a rim and filled with air.