I know you may think I might be a wierd person for saying this, but the most awesome excuse that is true however is when I was at my friends house and his mom was asking me what I'd like to eat for lunch and I said tacos and she asked me if there is anything I'm allergic too and I said " Yeah, I'm allergic to cheese because its made out of out dated milk."
I once dropped my phone into a fish tank whilst taking pictures of fish and I knew my mom would be really mad so my brain came up with a last second excuse when she asked me how I broke it.... I said I dropped it down the toilet xD