Poor letter spacing can ruin (or make hilarious) even the best thought-out text, as these examples demonstrate. If these mistakes are not the result of an errant space, then they might be result of automatic “kerning,” which is the process of adjusting the spacing between characters.
When type was printed using cast metal, parts that needed to overlap adjacent letters hung off the edge. Computer typefaces might have manual, automatic, or no kerning whatsoever; no kerning can make it appear that there is a space between letters when there, while automatic kerning produces mixed results.
(h/t: justsomething)