Kate, 33, looked ecstatic arriving at Ealing Studios in west London where the show is taped. Sporting a cream Jojo Maman Bebe babydoll coat and black heels, the eight-months pregnant Kate was greeted by writer and show creator Lord Julian Fellowes, before visiting make-up artists, costume designers as well as production, editorial and Ealing studios staff.
She also got to watch scenes being filmed in the servants' quarters and in the "Video Village" area, while meeting cast members Michelle Dockery (Lady Mary), Joanne Froggatt (Anna), Hugh Bonneville (Robert), Elizabeth McGovern (Cora), Phyllis Logan (Mrs Hughes), Robert James-Collier (Thomas), Lesley Nicol (Mrs. Patmore) and Sophie McShera (Daisy Mason).
Of course, the show couldn't have Kate leave without a few unique gifts to remember her visit. She was adorably presented a wooden train for her one-year-old son -- Prince George -- by Master George Crawley himself, who was accompanied by Dockery, his on-screen mother.
A delicious chocolate cake given to her by Nicol and McShera was also part of the festivities.
Finally, the unveiling of a plaque to commemorate the visit and an official photograph with cast members, writers and producers finished off her eventful visit.
In November, Kate and Will actually met British boy band One Direction before the Royal Variety Performance in London. Watch the cute moment in the video below!