My kid is freaked out by Santa!
Back in November, we were preparing Josh for our move by telling him he would get to pick the color of his new room. Josh told us he wanted bunk beds. We said he could ask Santa, and if he was good, he would get them. he was all excited about it. We prepped him for sitting on Santa's lap. In a deep voice, I would say "ho ho ho, merry Christmas little boy. What do you want for Christmas?"
And he'd try to mimic the deep voice and say "a bunk bed". So the night before Thanksgiving, we went to the mall to see Santa. We were practicing in the car the whole way to the mall. He was all excited. We got to the mall, he saw Santa and flipped out. He was clutching at my wife (not the way Tony clutched her in that pic). He was so scared he started to shake! Anyway, he didn't want to go see Santa at all.
Just know that you're not alone. A lot of kids Josh's age love TV characters and special characters in books, holidays, etc..... but freak out when they meet them in person.
I had a similar incident when my son was 2, only this was with Winnie the Pooh at Disney World.