Simpsons Season 4, Episode 17: Last Exit to Springfield

After learning that Mr. Burns' decision to revoke their dental plan has coincided with Lisa needing braces, Homer convinces his coworkers not to give up their dental plan and becomes the new head of the workers union at the Springfield Nuclear Power Plant. He holds talks with Mr. Burns, but these go badly because Homer is not intelligent enough to understand Burns' sly innuendos.