English tip #0 - One trick pony & Cry wolf

Heard on some YouTube video quite funny label of a person "One Trick Pony" - a person or acquittance with one talent (or a very few).

Just for reference:

• Urban Dictionary entry.
• Wiktionary entry.

And on the same video an another idiom: "Cry wolf" - a person rising false alarm as it is defined by wikipedia and thefreedictionary.