celebritiesandmovies: The joke that Bender tells but never finishes (while crawling through the ceil
celebritiesandmovies: The joke that Bender tells but never finishes (while crawling through the ceiling) actually has no punchline. According to Judd Nelson, he ad-libbed the line. Originally, he was supposed to tell a joke that would end when he came back into the library and said, “Forgot my pencil”, but no one could come up with a joke for that punchline. -- source link