Sometimes, I play a level in Transformice and it looks like a bridge is falling or a mouse dies, but its all there. This is annoying because I die and really, nothing happens!
SERIOUSLY!

What you are experiencing is called lag. It means that either your internet connection is bad (you can test this by writing "/ping" without quotation marks into the chat, if you get a number that is higher than let's say 100 your connection is bad) or that the internet connection of the shaman (who is determining the position & velocity of objects) is bad.