Pikachu, as comical as it is, there's a reason:
When Tyler was around 5, his class had a Class pet Pokemon, which was a Pikachu named Dracula, because it had its two front teeh showing all the time. It was a real loving Pikachu, always caring for Tyler and the other classmates, however, as they were going over its Pokedex entry one day, Tyler picked him up and a kid who heard they bite, decided to pull on its tail
That's when hell broke loose when Drac bit onto Tyler's wrist and refused to let go, when Tyler cried and try to push away, it freaked Drac out, so he used Thunderbolt on him and the other classmates, being point blank range, it affected Tyler the most

After Drac was banned and had to live with the teacher, Tyler never saw Pikachu or any Pika clones the same afterwards. He has the scar on his wrist to remind himself as such, he jokes around that it was "Super effective" on him, but he freezes up when he hears a Pikachu call, he can't even touch one. Though if it belongs to a friend he trusts, he'll try, and I mean try to not freak out