In the climactic fistfight at Armando's hacienda, West gets belted and hits the ground. Jim gets up and runs across the room to take out one of the baddies. Take note of the fact that the rear of his pants have split - right up the seam.
This is Ross Martins (Artemus Gordon) return after recovering from a near fatal heart attack.
At one point, West sees Artemus alive after believing he was dead. This scene is highly symbolic of Ross Martin's return from having a heart attack that had kept him off the show for several episodes.