Sons of the Pioneers (1942)

Night raiders are burning down the ranchers' barns and poisoning their cattle. Sheriff Gabby, unable to cope, goes east to get help from Roy, descendent of two famous sheriffs. Roy is a young entomologist who would rather study bugs than strap on guns. He finally gives in to Gabby's wishes and ends the terror.

At 00:45, in the opening scene of the movie, George "Gabby" Hayes juggles 3 cups.

At 46:50, Gabby juggles 3 bottles of nitroglycerin in 8 shots, and says he does not know how to stop.

At 52:43, in the final scene just before the closing credits, Gabby again juggles 3 cups.