When you accidentally press 'I' instead of 'U' or vice versa. It can lead to a lot of confusion and misunderstanding.
Person 1: hey man how are I?
Person 1: u*
Person 2: SWUTCHED!
Person 1: Did I get what I sent you?
Person 2: What? Are you drunk or something?
Person 1: Oh sorry, I swutched myself.