The one time I've managed to injure myself was a cake sitting thing a friend wanted me to do. Where it went wrong was, when the top part of the clear plastic thing cakes come in was removed the bottom one was left behind. Everything was just fine until I put my hands down to keep the cake from moving around and the thin plastic cover gave me a nasty cut on a finger. I kept going because I didn't want to ruin things but a deep cut + cake and icing being rubbed into it hurt way more than it should have!
Lesson learned, make sure both parts of the packaging the cake comes in are removed first!
Not only cake smashing, but pie throwing as well, as Lenny and I found out a couple of times in the 1990's when we were shooting pie scenes at my old ranch in Jupiter.
Lenny insisted on throwing the pies at the girls, but he had to stand at least 6 feet away otherwise his throwing arm would be caught by the camera lens. This was a problem when Hurley Coward came to my ranch to shoot some pie scenes, he wanted to stand far away so as not to be caught on camera, but his aim was off when it came to throwing pies at Jo Bache. He was off target 3 times and only hit the side of her face or chin. Lenny was usually well on target when throwing pies at the models, but the problem came when one day we ran out of our normal supply of custom made Publix Bakery pies (which were just perfect and held together under the hot sun). So Lenny improvised by creating some quick home made pies made from baking shells and filling them with whipped cream. The problem was those shells would crumble and fall apart and were unstable for throwing so Lenny made the decision to throw them with the tin foil plates on, to prevent them from breaking apart. This was a bad mistake because you should never throw pies with their tin foil bases on because one of them hit Melanie and the tin foil cut her lip. It was only a minor injury but Melanie was pissed and chased Lenny all over my garden and she wrestled him to the ground and gave him a piece of her mind.
I have the entire thing captured on video, it was like watching a Benny Hill chase all over my garden ... pretty funny, and that wayward pie cost Lenny $800 because in order to make it up to the girl he took her to the shopping mall the next day and bought her a designer dress and handbag.
That event caused us to make some changes in our pie shoots, and from then on we did less and less "pie throwing" and we opted to do more "pie placement" scenes instead, i.e. letting the other girls pie each other instead of throwing the pies.
I am sure Rich from Slapstick Stuff will agree, once you start to shoot many pie scenes and you make a few mistakes, you have a great deal more admiration for the mastery of The 3 Stooges.
Lenny told me many of the crazy tales from his shoots. I believe Asia Carrera either got a cut or hurt nose and was pissed at Lenny. Although she wasn't thrilled to be there, demanded a crazy sum to attend, and was antisocial when camera stopped rolling, back to her hotel while the rest went for dinner.
I wondered if there were any injuries in pie fights such as Three's Company Bakeoff, they really smashed those pies into each others faces, with tin pie plate.