This really occured;
Scene:1988, LAX at about 0200hrs, IMC, in a Army H60 without a lot of extra fuel....
US: R23643
Them: LAX approach
PIC (me) flying the aircraft, slightly off assigned altitude (4,150, should have been 4000)
LAX approach: "R23643 say altitude"
PNF: (before I could stop him) "Altitude"
LAX approach: (Ready to play the game) "R23643 say cancel IFR"
Me: "Sorry about that, R23643 4,150 correcting to 4,000"
We had a talk afterwords.
Jerry