A foam generator includes a container having a liquid. The container includes a container neck. A bubble generator is mounted to the container. The bubble generator has a liquid piston and an air piston that are mechanically connected together to simultaneously dispense the liquid and a flow of air. The liquid piston extends into the container as a bubble generator input stem. The liquid is received into the bubble generator input stem at a liquid piston intake of the bubble generator input stem. The air piston and the liquid piston feed both air and liquid to a mixing chamber that provides both air and liquid to a pair of mixing screens mounted on a bubble generator output stem. The bubble generator output stem is oriented below the bubble generator input stem. An inverted straw cover fits over the liquid piston intake of the input stem.