I have two favorites. One is when a sim is totally devoted to and wishes to marry their partner right after they already got married to said partner. I guess they really enjoyed the wedding ceremony and wish to experience it again, or think the next one will be better? This one is possible to fulfill if they break up first, observe a suitable cooling off period, and then re-marry, but I've never bothered going to that extreme and just dismiss the wish as a passing fancy or something that appeared by mistake out of the usual order of things.
The second one is when a teen draws the wish to learn how to drive, but they already have learned that, have the certificate proudly hanging on their wall, and have been driving their own or their parents' car all over town enjoying their new found freedom. This one I don't see how to (re)satisfy and was convinced it was a game programming problem until another player at MTS suggested that maybe it was really expressing a need to bond more with their parents, who would presumably be the ones teaching them how to drive (again), and that after a certain age these parents might have "forgotten" that they just went through all of this stress and horror. :D
Those are unusual exceptions though, usually for me the wishes drawn and especially the ones that appear in sequence make much more logical sense.