I guess many people may have seen this. I'm sure it could have a place in a numeracy class, and I'm quite enjoying thinking of the ways that might work: Why can't it work? Why is the answer not sensible? Estimate what a sensible answer might be. Let's compare it with the ways we have discussed doing these things. Is it right to check the answer? How does place value fit in? There's a lot you can do with it.
I used to hate Abbott and Costello when I was a teenager and they were all over TV and film shows. However I find this convincing and their timing is great.
You can find the video
here at Teacher Tube, and you may find the comments helpful. There's another similar clip
here.