One way is to use positive reinforcement. When your dog refrains from licking inappropriate areas, immediately praise it and give it a treat. Another method is to redirect its attention. For example, if it starts to lick something it shouldn't, offer it a proper chew toy instead.
The dog collar can be a plot device. If it has special powers, it can change the course of battles. For example, if it can create force fields, it can protect the dog and its owner from enemy attacks.
One way is to simply distract the dog. For example, when you see the dog approaching the cat with the intention to lick, call the dog's name and offer it a toy or a treat. This redirects its attention away from the cat.
Once, a girl was alone at home. A stray dog came into her yard. It started licking the window. As night fell, it continued. The girl was terrified. She could see its red eyes and slobbery tongue through the window. Every time she tried to look away, she heard its growl and the licking got louder, as if it was trying to break through the glass.
There was a haunted house in a small town. People said that a dog's spirit haunted it. One night, a group of teenagers dared to enter. As they walked through the dark corridors, they heard a low growl. Then, a dog appeared out of nowhere and started licking the feet of one of the teens. The licking was ice - cold and the teen felt a sense of dread. The dog's form was transparent in some parts and it seemed to be trying to lead the teen to some unknown and terrifying place.
I'm not sure if there is a specific common story exactly like that. It could be a very strange or unique scenario that someone might create in a fictional or very specific context.
Once, a dog licked my hand in a really creepy way. It was at an old, abandoned house. The dog's eyes were dull and it licked my hand so slowly, as if it was sizing me up. I felt a shiver run down my spine because the place was so desolate and the dog seemed out of place. I quickly pulled my hand away and ran.
Yes, there are. For example, a girl might be sitting in the park feeling sad. A friendly dog comes up to her and starts licking her hand. It's a simple act but can bring a smile to the girl's face as the dog's affection is so pure.
I'm not sure if there is a specific fanfic with that exact concept. There are countless My Hero Academia fanfics out there, and while some might have unique takes on Izuku's character, this particular idea seems rather unusual. You could try searching on popular fanfic websites to see if it exists.
The desperation. A licking dog in a scary story is often so desperate for someone's attention or love that they will go to any lengths. This blind pursuit can lead them into dangerous and haunted places, like an old, spooky house or a desolate forest. It's the fact that their obsession overrides their common sense that makes them scary.