
Marmaduke has been hypnotized by Neighbor-Man's potbelly. Unfortunately for Neighbor-Man, Marmaduke has not been hypnotized into thinking he's a chicken, but into attacking anything that comes into his field of vision, much like Christian Bale.
xy Explains Marmaduke

The Anderson's are aware that a product called 'Xbox' exists and that it was once popular among children. They are not aware that no child alive today would actually want an Xbox and than if even if one did possess such an item, they would never trade it for a dog. Especially not one that has homicidal tendencies.
Marmaduke is terrorizing an unknown man. This man, besides being a Jon Meacham fan, is wholly unaware that Marmaduke is not a visitor and is, in fact, a demon spawned from Satan's own loins.
After having been denied for his previous loan, Marmaduke is now trying to scam the student finance branch of 1st Bank. Marmaduke has also increased in mass again in an attempt to look more imposing to the loan officer in the hopes of being approved for his 'school' loan.
Marmaduke has increased in size by a factor of 2 but Zelda the Clairvoyant/Fortune Teller/Palm Reader doesn't see this as a reason to acquiesce to his request. Probably because she an ex-con on parole for palm-reading fraud.
Marmaduke is running a Hotel for Dogs. This hotel will be more like the Bates Motel than the one from the children's movie except for the men-in-women's-clothing and mummy angles.