Humorous word misusage
A couple weeks ago I was musing about how much more entertaining the world would be with more accidental word misusage and replacement. I was reminded of that tonight while I was working on a paper. I typed "elf-consciousness." That led me into a whole giggle frenzy (I've been working on this paper for a long time, now, and my sanity may be taking a short vacation) as I imagined the world suddenly preoccupied with "elf-awareness", "elf-esteem", "elf-expression", "elf-examination", "elf-development", etc.
One word mix-up that would be really funny: "fromage" and "frottage". Accidentally demanding that the waiter serve you more frottage would be an embarrassingly amusing situation- especially if you were trying to impress your date with your mad French skillz.
Of course, there's always the old bio class standby: the confusion of "organism" with "orgasm". (Heehee, shout-out to Vilhelm)