Lag is a common occurrence in many online games, where the game will noticeably stutter. This can cause a majority of issues with players as it can prevent people from getting anywhere depending on how bad it can get. In Transformice, lag can cause mice to fall through platforms, usually to their death. Lag can also cause the Anvil God to suddenly change its position and mice to die and come back afterward.
Another effect happens at the start of the game. Lag might occur as the game attempts to keep up with the server and rushes through events that have already happened on the Map. A common effect of this is prop-doubling (double trampolines, double Anvil God, etc.), anchors not working for pre-anchored items, or rare occasion, map items not spawning at all.