One-Trick Pony: (Noun) A person or thing with only one special talent, or area of expertise.

Oh wow, what a surprise. Lindsay Lohan. Doing Marilyn Monroe. Again. This time for Spanish Vogue. I guess she likens herself to the fallen star since they're both troubled, substance-abusing actresses with a poor work ethic and questionable talent known more for their scandalous personal lives rather than professional resume. But then again, Marilyn Monroe made like fifty films lived to be thirty-six. At the rate she's going, Lindsay's life expectancy isn't going to be near that high. She's probably be better off relating herself to the dog from the Air Bud movies at this point.