Lemons

Lemons are never seen in game, but are mentioned in the 1980's test chambers by Cave Johnson. Not much is mentioned except for a discussion on the aphorism "When life gives you lemons, make lemonade." Cave tells you to "Get mad," and to "Make life take the lemons back." The lemons are also mentioned by the Oracle Turret. The Oracle Turret tells you to "Get mad" and "Don't make lemonade". Cave Johnson also tells you that "He's Cave Johnson, the man who's going to burn your house down. WITH THE LEMONS! GLaDOS says that she likes this man, shortly before she figures out who she is.