Tip 1: Always blame your cat for the mess you made. It's purr-fectly reasonable to assume they were the one who ate the last donut.
Tip 2: If you can't remember what day it is, just tell people it's "almost" Friday. They'll never suspect a thing.
Obstructive Excuses
If you're running late, just tell them the bus (or train, or spaceship) was cancelled. You're not really late, you're just "adapting" to the situation.
If you can't do it, it's not because you can't, it's just that the project was "incompatible" with your schedule. That's a real thing, right?