Cassie Come Home - S5.E4

Janet's mother Ella becomes a trainee JP. When visiting Janet and George she comments on the fact that Ollie hasn't spoken a single word yet. He responds by talking a language that sounds like baby talk (George has been teaching Ollie the language of Jupiter). With Ella's thoughts in mind, George goes out to get some educational stuff for the kids, he ends up getting porn for them and giving Ollie a cigar and alcohol. Ella takes Ollie and Cassie away from Janet and George but without them Cassie reverts to being a normal human.