'Putting Lipstick on a Pig' is a rhetorical term generally used in reference to someone who's trying to make cosmetic or superficial changes on himself that clearly doesn't deceive anyone.
Example of use: Marla – "Did you see Susan's new hairdo? I guess she thought that cutting her bangs and coloring her hair bright orange looks good." Joe – "Oh please, it's like putting lipstick on a pig."
The connection between pigs and lipstick goes back to 1926, where the editor of the Los Angeles Times, Charles Lummins wrote: "Most of know as much of history as a pig does of lipsticks." However, the first recorded use of the phrase as we use today, was in a 1985 article in the Washington Post, regarding plans to renovate a Park in San Francisco: "That would be like putting lipstick on a pig."