In the episode where Arnold tries to teach Gerald how to bike. Gerald tries to learn how to bike fast but swerves out of control when a kid passes by him. Gerald hits a trash can which says "Keep our park cleans". What kind of government or society would misspell a simple public message?
In the episode where Arnold tries to teach Gerald how to bike. - This is not even a sentence as it does not contain a primary clause.
Gerald tries to learn how to bike fast but swerves out of control when a kid passes by him. - "Bike" is not a verb. "Fast" is a noun, not an adverb.
Gerald hits a trash can which says "Keep our park cleans". - Trash cans can't talk. Perhaps a sign on it read "Keep our park cleans".
The government makes all kinds of grammar mistakes. For example: the sign that says "Slow children at play" is grammatically wrong. It states the children are slow, as opposed to driving slow.