There have been gnomes in every episode of The Sims since episode one. In the first episode you could craft gnomes in the woodworking table. If you had the ‘makin’ magic’ expansion pack you could cast an enchant spell on them they would look after the garden for you by watering plants and things (until the enchantment wore off). They took casting the perfect garden spell as a personal affront and would get very angry if you cast it and kick you in the shins and trash your garden.
These gnomes could be found in Sims 2 and 3 as well. In Sims 3 they could even have baby gnomes, although that might have required the generations expansion. In the Sims 2 there was also a gnome called Shifty Sam who would shift about when you were not looking and end up all over the house. Much the same thing happened in Sims 3 only he is generally referred to there as the Mysterious Mr Gnome. With The Sims world adventures expansion pack came various ‘foreign’ magical gnomes such as Master Manchu from China, Sultan Sam from Egypt, Little Leon from France (who looks like Napoleon). With the Ambitions expansion pack come the magical gnomes of invention, sculpting, laundry and B.C. whilst the late night expansion pack brings with it the magical hip-hop and vampire gnomes.
In Sims 4 (the current incarnation as I am writing this) there seem to have been some retrograde steps when it comes to gnomes. No longer can you see the little gnomes walking about or looking after your garden. There are an assortment of gnomes you can buy and at least one you can find and they do disappear and reappear like Shifty Sam but at the moment that is all they do. There are a number of gnomes to buy, Happy Gnomiversary, Guardian of the Gnomelaxy, Bearly Gnome, There’s no place like Gnome, Happy Gnome Garden Pal, Gnome matter what, I’m Still your baby, Don’t Fear the Reagnomper, Mr Floppy the Gnome, The Ghastly Ghostly Gnome, Poolside Gnome, Strictly Business Gnome, and Bare Essentials Gnome (from left to right in the above picture). There are a few more that are filed under kids decorations rather than outdoor sculptures such as the one with the gnome riding the pink flamingo.