During the montage, George comes home to find it a mess, the stair railing covered in drool, and finding Beethoven completely drenched in George and Alice's bed, and shakes himself dry, getting George and the rest of the room all wet.
Ted standing up to a gang of bullies who are haggling him right in front of his house, unaware that Beethoven is standing nearby and baring his teeth for them all to see. The bullies give Ted his glasses back and immediately back off; that night, and Beethoven bails back home. That night, Ted is mugging for the mirror while shirtless, showing off his muscles.
Beethoven being taken in for a routine checkup when the vet's assistant walks in to give him his shots. Beethoven sees the syringe and faints on the examining table!
Beethoven crashing George's dinner meeting with Brad and Brie, dragging them both by the leash while they're still in their chairs, taking the deck table with them!
In one scene, the kids are playing video games and if you look carefully, Ted is playing with the Power Glove, a Nintendo controller that was notoriously difficult to use and a major flop on release.
The second film:
Beethoven's dream at the beginning. The family is giving him all kinds of food culminating with George giving him a giant steak.
At the start of the film, George is so busy monologuing that when the newspapers kid throws the newspaper at him, he accidentally knocks the coffee he's drinking, staining his suit.
Then when he comes back later, George preemptively puts his coffee mug aside so he can catch it safely. The kid throws the newspaper... and accidentally breaks one of the hanging pots above George's head, covering him with earth. The boy can only say a feeble "Sorry" before leaving.
When the family stops by the drive-through of a McDonald's, George and Alice are so busy talking that Beethoven is the one who orders for them!
Beethoven covers his eyes when he sees George dancing to "Do You Love Me?"
Crossing with awesome: when Beethoven gets fed up of the drunk teenagers pouring beer on him, he pulls his chain hard enough to break the balcony's support beam, sending them all into the lake. Even more: when Ryce's boyfriend ends up falling himself, he lets out a Howie Long Scream.
The burger-eating contest. George got himself dragged into it, so he's taking his time to eat the burgers. Then a couple kids in the crowd start mocking him, he gets angry and after exchanging a look with Beethoven, he proceeds to speed up his eating.
While cheering on George and Beethoven, Alice briefly reacts with disgust at the current champion's Jabba Table Manners. Even more during the last seconds, the guy tries to force the last burger by punching it into his mouth!
George manages to win the contest, but predictably, he needs to throw up almost immediately, forcing him to rush to find a bathroom.
Regina and Floyd's whole chase of the puppies across the mountain is full of funny moments. To wit:
The pair walks across an old bridge, which halfway through breaks under their weight. Then one of the puppies comes to check on them, and when Floyd looks up... the puppy pees on him.
Later, while crossing a thin log across a wide chasm, Floyd loses his balance and ends up rolling downhill, landing headfirst on a stump. He walks back up and asks for Regina's help to remove it, and she does... and now she's the one rolling downhill herself. Rather than helping her, Floyd just yells "Thanks, Regina!"
Their ultimate fate: Beethoven shoves Floyd with his own stick right into his crotch, pushing him off the edge. Regina tries to grab him and they both fall into the muddy pond down below. The two start fighting so much that they end up pushing the wooden dam off the pond, and are dragged down into the raging river, still yelling at each other as they are pulled quickly downstream into the distance. Alice, who has been watching them with concern, then turns to her family and asks "Well, are you hungry?"