OP here - I was all prepared to believe it was molar teething, since he seems to get teeth in batches of 4 and the last batch came about a month or six weeks ago.
HOWEVER, I called my ped's advice nurse after posting her to plead for any advice she might have and she unexpectedly offered me an appointment. Honestly I figured it was a waste of time but it turns out the little monster actually does have an ear infection. Last week, the ped who saw him only did a timpanogram and never actually examined my son's ears. I am not happy about this, except that I do recognize my son was in very happy charming form at that moment and I was perfectly persuaded that the normal timpangogram meant that it wasn't an ear infection. The ped even joked about it, saying I know you were probably hoping it was something treatable as opposed to teething, nightmares, etc and asked sort of humourously if I believed him (of course I said yes, as I did).
Today we saw a different ped in the practice who examined him closely and noted that one of his ear drums wasn't visible due to a big chunk of wax (yuk, sorry.) She removed it and found a raging ear infection. I'm posting just as a PSA to other parents - I learned a lesson to always make sure the peds examine the baby him/herself! We've been down the ear infection route lots before and I was told the timpanogram was very reliable, but evidently it doesn't work well with waxy ears. Sometimes I feel like a PITA bringing in one of my kids when they're not desperately ill, but I've had a bit of a wakeup call with this experience.
To the PP with a 14 month old daughter going thru separation anxiety, is there any chance that you use a DC-based daycare with a half day tomorrow? I'm curious only because my son was moved up to the toddler room with another little girl! Either way, good luck to you and all the fussy 14 month olds!