My favorite sign mix-up is one my sister showed us in the Weird NJ magazine(I know, it's redundant) she brought to Texas. Someone removed the first G from the ad outside for Black Angus Burgers.
uh oh.....ROR!
LOL!
We had one of those restaurants across from where we used to live, and someone pulled the same stunt with their neon sign.
It took 'em a couple of weeks to fix it. I laughed every time I passed by.