During the opening, old 1930's cartoons are played on a giant monitor and are different each time. In the episode "Roswell That Ends Well", the cartoon featured in the opening was played in the episode on a small TV. Also when the title appears, a new message appears every time.
Though the cartoons shown on the giant monitor are usually old, vintage cartoons (most likely public domain), on at least one instance a clip from a Simpsons short (from the Tracey Ullman Show) was used (Matt Groening created both Futurama and the Simpsons).
Occasionally, before the opening credit sequence begins, the show will be "sponsored" by a futuristic sponsor advertisement. For example, "Futurama is brought to you by Glagnar's Human Rinds." The show always begins with a parody of the "Transmitted in SAP" type of show disclaimers when the title "Futurama" appears. For example, "As Seen on TV" or "Present in BC (Brain Control) Where Available".