The loneliness of the comfortable material life vs. the support and reassurances (and disadvantages) of the large family life get their treatment in a rather moving scene. The city-mouse hero, who was catapulted from comfortable isolation into a teeming, streaming water-world of the London Sewers (the joke where he clutches in panic what turns out to be a candy bar in his descent is priceless), sees through a closed window the heroine's teeming, oddball family and begins to realize that what he had, what he lost, what he wants to get back to--may not be worth very much. And he does have to make some very tough decisions.
Some bracing profundtiy swirled in with a great many hilarious jokes and gimmicky schtick that you have to think back over to appreciate all the humor. The two amphibian villains--the Toad and Le Frog-- are caricatures that go right for the throat of British and French culture, but, no fear, we Yanks get a good pronging, too, and the Royals, and the Proles, and the Soccer fandom... As long as the guns rotate 360 degrees, I'm cheery.
Two strange worlds--London's sewers, and lower-class English life. Lots of boats and some snappy humor and some shameless, glorious sight gags. Fairly good computer animation with lots of eye-candy, and a chorus of singing slugs. Yes, it stands out, it is not more of the same, and is good for multiple viewings.
Just don't leave the seat up.