This is the first Gnomeo & Juliet film to be rated PG by the MPAA, unlike the first film which was rated G, despite that film also having been labelled for "Some Rude and Suggested Humour", and releasing after the MPAA got stricter in 2010.
Both Gnomeo and Juliet films were directed by someone who directed an Oscar Nominated Dreamworks Animation film. Kelly Asbury, the director of the first film directed Shrek 2 (2004), while John Stevenson, the director of this film directed Kung Fu Panda (2008).
Both Chiwetel Ejiofor (voice of Gnome Watson in this film) and experienced voice actor Jim Cummings (voice of Featherstone in the first film) were in an iteration of The Lion King, which also had music done by Elton John. Cummings had been in the original 1994 animated film as the voice of Ed, whilst Eijofor had been in the 2019 live action reboot as the voice Scar.
Both this and the first film had a one year gap between the release of a film in Disney/Pixar's Toy Story franchise. Gnomeo & Juliet (2011) came one year after Toy Story 3 (2010) whilst Sherlock Gnomes (2018) came one year before Toy Story 4 (2019). Both of these franchises are about inanimate objects coming to life whenever the humans aren't around.
One of the 2 Sequels to a 2011 Film that got Rated G by the MPAA to have a different rating. The other one was Alvin and the Chipmunks: The Road Chip (2015), of which was PG instead of G much like the first 2 films in the Live Action Chipmunks film franchise had been, unlike Rio 2 (2014) and Cars 3 (2017) which were still Rated G like their 2011 predecessors.
The trivia items below may give away important plot points.
When Sherlock Gnomes and Moriarty fall off London Bridge, blue fireworks go off behind them, resembling a pouring waterfall. This is a possible nod to the Sherlock Holmes short story "The Final Problem", where Holmes and Professor Moriarty fight on the ledge of the Reichenbach Falls, and are assumed, by Dr. Watson, to have fallen to their deaths during the struggle. The short story was meant to author Arthur Conan Doyle's end to his Sherlock Holmes stories, by having his hero killed off. Years later, Doyle gave into popular demand and revived the famous slueth the short story "The Empty House", where it is revealed that Holmes didn't die in the fall, but instead went into hiding in fear of being targeted by Moriarty's henchmen.