The second entry in the Batman Unlimited series, Monster Mayhem, is, if nothing else, a well animated entry. Sadly, there's not a whole lot of other positive things to say. Make no mistake, this isn't a bad film. It's just that the movie is targeted strictly at kids and seems to make no effort to attract adults. That's not a bad thing, but it's a shame no effort was made to try and reach a wider audience. Between this film series being strictly for kids and the thrice annual DC Universe animated movies which are targeted at teens and adults, there's little in terms of DC animation that appeals to all ages.
The bonus features are a nice treat, however. Like the first movie, this release has a selection of DC Nation animated shorts. Notably, the Green Arrow shorts are here along with others including Animal Man and a great Riddler short. There's also the standard video feature (this one on the look of Gotham City and the visual cues taken from Batman Beyond), along with a bonus episode of Batman the Brave and the Bold, and some trailers.
All in all, the movie is worth it to add more DC Nation shorts to your collection. I know that's why I bought this and Animal Instincts. It sure wasn't for the movie.