Marmaduke needed to retrieve his bone, and when Marmaduke needs to retrieve his bone the last thing he cares about is whether or not he is ruining a child's afternoon in the process.

Marmaduke is trying to tell his fat, elderly neighbors that he is going to kill and eat them. The hole in the screen is entirely incidental.

Marmaduke ate the mail.

Marmaduke has gained new corporate sponsorship.

Marmaduke is riding a skateboard. While this in and of itself is absolutely HYSTERICAL (dogs aren't supposed to be able to ride skateboards!), the gag is kicked into overdrive when it is revealed (via his owner-boy's exposition to his fellow tricycle enthusiast) that not only is Marmaduke a dog who can ride a skateboard, he is a dog that is phenomenally skilled at riding a skateboard. You could cut the comedic absurdity with a knife.

Marmaduke is licking his owner-boy, who tries to pass off dog saliva as hygenic.