Apparently, Ebert and Siskel despised each other in the beginning. They came from very different backgrounds. Ebert's father was an electrician and Ebert attended the public school University of Illinois. He went on to be the first movie critic to win a Pulitzer. Siskel was a Jewish kid who became an orphan at age 10. He attended Yale and hung out with Hugh Hefner quite a bit. These outtakes are hilarious, especially when they start ragging on Protestants.
Finally, a classic. Howard Stern interviewing Siskel & Ebert around 1990. I found it endearing when Siskel admonished Ebert not to disclose Ebert's girlfriend's age. Real brothers.