Tonight in New York they played the episode "The Phone Message". In between the opening monologue and the 1st act, (an actual) Dockers (pants) commercial aired. Into the first act was the start of the ongoing argument between Jerry and Jerry's girlfriend about a Cotton Dockers commercial.
Although it didn't bother me, I thought the airing of the Dockers commercial was significant in that the disagreement about the Dockers commercial was part of the sub-plot in the episode.
Has anyone else noticed an airing of a commercial during a Seinfeld episode where that product is mentioned in the episode you were watching?