How likely are these deaths?

1. When the woman ate a pizza topped with Ink Cap Mushrooms, and drank alcohol, which killed her because these mushrooms release a toxin when in contact with alcohol (I checked, and you need to wait something like four to five days before drinking again if you eat these mushrooms).

I am mostly asking if it's likely for a pizza (a store bought one), to have these mushrooms; I had a pizza with mushrooms on it last night, and I want to know if it's likely that it was Ink Cap Mushrooms - it just said mushrooms.

2. The man who was bouncing on his computer chair and part of the chair shoots up and impales him. I don't bounce on my computer chair, of course, but if this is possible would it only happen if you were bouncing like he was, or could the slightest movement cause this to happen?

Please answer soon (I'd like the mushroom one answered today if possible, sorry to be pushy, but I'd seriously appreciate it).