I've always had this problem. ANd then once their stuck, I'm humming all around the house.
DH thinks it's funny, so he'll hum a few notes of some really dumb song (like, oh, The Oscar Mayer Balogna song) then just wait paitently -- sure enough, give me a minute and I'll have it stuck in my head and be humming it!
Ugh! THe tricks a DH learns to play on you in 20+ years - just no fair, LOL!!
I once had to go out to Cincinatti and install some expensive electronics. The customer didn't want this stuff trusted to a freight carrier, so another engineer and I had to drive it there in a rental truck and install the stuff over the course of a week.
The fellow I was stuck riding out there with and working with all week got it into his head to sing the "WKRP in Cincinnati" TV show theme song all the time, and I do mean all the time. I was ready to kill him, and I'm not sure they'd have been able to find a jury to convict me.