In the 6th season episode "The Extra Job", unknown to Lamont-Fred find a job as a busboy in a restaurant to help Lamont financially since he is getting married. When Fred decide to quite in the middle of rush dinner hour, his boss tried to intimidate him by calling one his big muscular kitchen cook to stop Fred from leaving.

According to Labor laws, that in an illegal act and manager could have got easily sued by the employee. But I guess it didn't matter in this case since Fred was a lousy Busboy to begin with :D

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