Spike is a burly, gray bulldog wearing a red sweater, a brown bowler hat, and a perpetual scowl.
Chester is a Jack Russell terrier who is just the opposite, small and jumpy with yellow fur and brown, perky ears.
The cat is Freleng's own Sylvester, but every time Spike thinks he has the cat cornered, a runaway zoo black panther appears in Sylvester's place, thrashing the dog instead.
Chester, of course, never sees this transformed Sylvester, thinking his buddy is being beaten by the tiny tomcat.
The final loss of face for Alfie is his being thrashed by a fly that has also been affected by the potion, as it occurs in front of Chester's eyes.