Permanent Retirement

S1, E4: Grandpa, Gwen, and Ben visit an old maid relative only to find that her retirement community has been overtaken by a shapeshifting aliens called Limax. The Limax are systematically gathering the elder population for transport back to its home planet to use as a food source. Ben must use his alien heroes to defeat the Limax and rescue not only his matronly aunt, but Grandpa Max as well.