goof on (someone or something)
To mock or tease someone or make fun of something. Sarah's a very sensitive kid, so don't goof on her.
goof on someone
Inf. to tease or kid someone. I don't believe you. I think you're just goofing on me.
Make fun of, mock, as in He was always goofing on his little brother. [Slang; mid-1900s]