The sign on the bus indicates that the movie takes place in Stratford-Upon-Avon, birthplace of William Shakespeare, who wrote Romeo & Juliet, which is what Gnomeo & Juliet is based upon.
When Lady Bluebury tells Benny to "Unleash the dogs of war," this refers to a line from Julius Caesar, "Shall in these confines with a monarch's voice, Cry 'Havoc,' and let slip the dogs of war;"
When Featherstone starts to reflect on the memory of his mate, the female flamingo is on the left, however, when the moving van arrives to move the female, the female flamingo is on the right.