When Gnomeo and Benny sneak into the Red Garden, Benny says "I love going commando" This will fly over kids heads.
There are several adult jokes that will fly straight over kids heads "whose your gnomie" (as in whose your daddy). Also The frog character makes several dirty jokes, etc.
There are a number of very sexually suggestive comments: 1. Juliet says to a male gnome that his "Tulips look limp." 2. The frog asks "Is his... big and pointy?"
3. Juliet says "A squirrel dropped his nuts" and a the frog adds "Nuts the size of boulders."
A male gnome is seen bare-chested on multiple occasions and wearing bathing trunks. A male gnome is seen on multiple occasions wearing a thong-style bathing suit and his bare buttocks are seen on one occasion. A female gnome is seen wearing a mid-drift exposing shirt (we see cleavage) and tight, form-fitting pants. A male and a female gnome are seen washing themselves (fully clothed). The male gnome is seen rubbing his behind and washing his armpits.
A male gnome is stuck under a large bra, which is dragging across the ground. The gnome uses it as a rope to climb a chair.