Here are some outs I use when I screw up a trick....which is often
1. "jeez...that's weird, it worked in the magic store"
2. "Oops...did I say I was a magician? I meant musician! For my next song I'd like to play..."
3. "The real magician will be here shortly, I'm just standing in"
4. "It's all part of the show folks--the part that hasn't been rehearsed!"
5. "That's the first time that ever happened again"
6. "It doesn't look as bad from my side"
7. "I'm curious to see how I get out of this myself"
8. "What do you expect, I'm paid 3 dollars an hour, and don't even work for more than 10 minutes, you do the math"
9. "I knew I should've had decaf"
10. Stare blankly at the trick that went horribly wrong. Blink your eyes a couple of times really stupidly. Then throw it over your shoulder and practically yell "...AND FOR MY NEXT TRICK..." Then just go on with your routine.
11. If you drop something, "Wow, good thing the floor was there to catch that"
12. "I forgot to compensate for the rotational effect of the earth"
13. "Did... did I show you the (insert last successful trick) trick?
14. "Wait - COME BACK"
15. "Wow, its so quiet in here you could hear a career drop"
16. "That's what we magicians call misdirection, I pretend to mess up, and while I have your attention, my assistant sneaked by into the next room with an elephant for a trick I'm doing later. If you don't believe me, go check."
17. "There is only one thing this trick is missing... talent!"
Feel free to add!