Continuity mistake: When the Coyote is flying in his makeshift air balloon, there is a rope around the bin that keeps disappearing and re-appearing between shots.
Continuity mistake: When the Coyote emerges from the manhole with a hand grenade, you can see behind him there is a signpost. When we see the Road Runner passing through the road fast enough to drop a boulder on the cover, the signpost has gone, yet it re-appears in the next shot.
Continuity mistake: When the Coyote is curled up like a spring, he is holding a knife in his left hand and a fork in his hand. When he starts chasing the Road Runner, he now has the fork in his left hand and the knife in his right.
