Why quotes get misquoted

Beam me up, Shakespeare.

"Methinks the lady doth protest too much." -- not Shakespeare
"The lady doth protest too much, methinks." -- Shakespeare

"Beam me up, Scotty!" not Star Trek
"Beam us up, Mr. Scott!" -- Star Trek

"Play it again, Sam." -- not Humphrey Bogart
"If she can stand it, I can. Play it." -- Humphrey Bogart

Why do we change famous quotations?

Have you noticed how incorrect quotes often just sound right—sometimes, more right than actual quotations? There's a reason for that. Our brains really like fluency, or the experience of cognitive ease (as opposed to cognitive strain) in taking in and retrieving information. The more fluent the experience of reading a quote—or the easier it is to grasp, the smoother it sounds, the more readily it comes to mind—the less likely we are to question the actual quotation. 

Those right-sounding misquotes are just taking that tendency to the next step: cleaning up, so to speak, quotations so that they are more mellifluous, more all-around quotable, easier to store and recall at a later point. We might not even be misquoting on purpose, but once we do, the result tends to be catchier than the original.

So how do you spot that misquote?

There's (sadly) no effortless way to go about it. The most we can do is to always be skeptical of ourselves, especially if something sounds too right or fluent or spot on. Because the better it sounds, the more likely it is to be a little off. That, and check quotes before we perpetuate them in cyberspace or print. Otherwise, we might end up like Bob Dylan, who once remarked, "I've misquoted myself so many times, I don't know what I've said." (He totally could have said that, right?) 

Just remember: A quote in time must rhyme.