1. A login window or form appears
2. Enter username
3. Enter p-
4. Another application STEALS THE FUCKING FOCUS
5. Enter half of the (or the whole) password in the app that stealed the focus and press Enter by mere inertia

Or this variant:

4. The username field gets autofocused
5. Enter the password in the username field, out in the clear for everyone to see

DON'T YOU STEAL ME FOCKING FOCUS MATE