- "Biff picked up the cane that rested beside his feet. Marty noticed that the cane's brass handle was sculpted into a clenched fist. Biff lifted the cane and knocked it briskly against Marty's forehead."
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 31)
- "And all three of them, Doc, Marty and Jennifer, were busy elsewhere [the McFly residence], so none of them could see Biff take off in the DeLorean, or, a moment later, land the DeLorean in the exact same spot. He quickly got out to hobble away, too quickly, maybe, because his cane got caught as the gull-wing door swung down. The cane snapped in two as Biff struggled with it. He took the half he had freed and hobbled away, leaving everything like it was before — except that now Biff no longer clutched the silver bag."
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 92)
- "It's the top of Biff's cane. I mean Old Biff from the future."
- —Marty McFly in 1985A
As Biff's hands were now too feeble to hit anyone hard, the cane had a metal fist as a handle — upon which Biff's name, BIFF H. TANNEN, was engraved — which he would use instead to knock people on the head with.
When Marty McFly was posing as his son, Marty Jr., Old Biff used the metal-fisted cane to rap Marty on the head while saying "Hello? Hello? Anybody home?", in much the same way as had been done to Marty Jr.'s grandfather, George McFly, before him.
When Biff stole the DeLorean time machine to travel back to 1955, he took his cane, and left it behind in the car when he returned to the future. At this point, Biff was beginning to vanish from existence due to the new history he had created by giving his younger self Grays Sports Almanac. As a result, when Biff exited the DeLorean on returning to 2015, he suddenly clutched his chest in pain — causing the top of the cane to break off and fall inside the car — before staggering away, collapsing behind a stationary car and fading away.
When Marty and Dr. Emmett Brown left 2015 for 1985, the presence of the top of Biff's cane was unknown to both, and they found themselves in a nightmarish alternate reality. Only after finding the cane's metal fist handle, along with a silver-colored bag containing a receipt for Marty's earlier purchase of Grays Sports Almanac from the Blast from the Past antique/memorabilia store, did they realize what had happened.
Behind the scenes
- It is never explained on-screen as to how the top of the cane could remain behind if Biff (clothes and all) had faded out of existence.
- In the novelization (see second Quote above), the cane breaks in two when Biff gets it caught in the DeLorean's gull-wing door as he gets out on arriving back in 2015.