fell through the manhole cover
To drop the ball on a task, or to fail entirely at an assignment. Or to have done way, way, way too much cocaine the night before.
I can't make it in to work today because I fell through the manhole cover this last night like a total bone head.
Billy! Where's my report?!?! You fell through the manhole for the last time... you're fired!
Billy! Where's my report?!?! You fell through the manhole for the last time... you're fired!