The Rugrats are puzzled by the erratic behavior of Spike, who has stolen Angelica's play barbecue, Chuckie's shirt and Stu's franks and frequently goes under the house. The Rugrats thought Spike was under control of aliens from "the planet on Chuckie's shirt". The real story is that Spike has adopted kittens, his "babies". Meanwhile, Stu builds a japanese-style barbecue and a walkway, though he's having trouble keeping the babies out of the fresh cement. (thetvdb.com)