You had found the statue of Bill Cipher. You weren't supposed to shake the hand, but you did. Suddenly Bill appeared. He was a yellow triangle, with one eye and no mouth, he had his long black tophat and black bowtie on. He didn't notice you...yet.

Bill: "HAHAAHAHAHHA! HOLY HECK I ACTUALLY SURVIVED THAT PUNCH!"

He said,unaware of your presence. After he noticed you.