Another random probably short blog post on a topic which just randomly entered my head: Getting words wrong.
In songs, specifically. More common there, because one's concentration must be split between the words and the notes, whereas when just speaking you only have the words.
Actually, to be honest, I don't have much to say about the subject, I just feel like giving examples of occasions on which it has happened to me, in the hope that people will be at least mildly amused.
Of course, there's the obvious possibility of simply singing the wrong verse to a song. Most notable example being in the Act 1 finale of HMS Pinafore, when it's gone into 'A British tar'. Having been spending the time while the girls were singing concentrating on doing the hornpipe right, suddenly switching from that to "Ahh! We have to sing!" has problems and, yes, sometimes I sing the wrong verse. A couple of words in I'll probably be going "Wait, isn't this wrong?" but switching verse mid-line is really hard.
Then, naturally, due to our summer shows, which take music from G&S (And other sources) and change the words, sometimes I will mix up the summer show words and the actual words. e.g. In The Grand Duke, 'Your Highness there's a party at the door'. During the actual song I was fine, but when I heard the relevant excerpts in the overture, I was always internally going "The Marquis of Torpenhow? The Marquis of Torpenhow! Good gracious a plan that is sure to be seized at..." etc. Conversely of course, while reminiscing about How to Marry an Aristocrat during a rehearsal, I tried to sing the version from that, but switched to Grand Duke words partway through because they'd sort of over-written the HtMaA ones. And then back again a bit later.
On a similar note, I once, a day after seeing a production of The Mikado, while I was rehearsing HMS Pinafore, tried to sing part of the Mikado Act 1 finale, but found I was singing it to the tune of the Pinafore one. Specifically, I was singing "With joyous shout, with joyous shout and ringing cheer/ Inaugurate, inaugurate their brief career," to the tune of "This very night with bated breath and muffled oar/ Without a light as still as death we'll steal ashore," and it fits perfectly. Which was a tad confusing.
But of course the strangest examples are just odd word substitutions, frequently involuntary (If not involuntary, then usually rude). Examples which I have persistently come out with (Though fortunately never in performance):
In Iolanthe, 'A shepherd I'. The actual words are "Betrothed are we," but for some reason in my head it kept turning into "Deposed are we," or on one particular occasion, "Dispose of me," which, granted, a lot of the lords might be happy to do at that point, but still.
In Yeomen of the Guard, Act 1 finale, 'Oh mercy'. Actual words, "Of all immured within these walls, the very worthiest falls," but for some reason I keep thinking 'nerdiest'. If anyone is to blame for this other than me, it is the Vlogbrothers, but in any case it's rather odd imagining Colonel Fairfax as a total nerd.
I'm sure there must be others - in fact I have a vague recollection of making such a substitution and then checking myself because it reversed the whole meaning of the song... but I can't remember what song it was. Oh well.
Do any of my intrepid readers have any comparable examples they would like to share in the comments?