On learning George is Thermoman Janet's mother quizzes her about any physical differences. She looks astonished when Janet hints at his large 'body parts' yet has already seem him (and was transfixed that time) on seeing George naked in the shower in Season 1.
In Season 2 Episode 1 George states his age as 842 years old, but in Season 3 Episode 4 George states that his age is 327