Sales employee Bob wants a clickable blue button.

Bob tells product owner Karen about his unstoppable desire for clickable blue buttons.

Karen assigns points for potential and impact (how much does a blue button improve Bob's life, how many people like Bob desire blue buttons)

Karen asks the button team how hard it is to build a button. The button team compares the request to a reference button they've built before, and gives an ease score, with higher score being easier (inverse of scrum points).

These three scores are combined to give a priority score. The global buttonbacklog is sorted by priority.

Once every two weeks (a "sprint") the button team convenes, uses the ease scores to assign scrum points. Difficult tasks are broken up into smaller tasks, because there is a scrum point upper limit. They use the average of the last 5 sprints to calculate each developer's "velocity".

The sprint is filled with tasks, from the top of the global button backlog, up to the team's capacity as determined by velocity. Approximate due dates are assigned, Bob is a happy Bob.

What if boss Peter runs into the office screaming "OUR IMPORTANT CLIENT WANTS A FUCKING PINK BUTTON WHICH MAKES HEARTS APPEAR"?

Devs tell boss to shut the fuck up and talk to Karen. Karen has a carefully curated list of button building tasks sorted by priority, can sedate boss with valium so he calms the fuck down until he can make a case for the impact and potential of his pink button.

Karen might agree that Peter's pink button gets a higher priority than Bob's blue button.

But devs are nocturnal creatures, easily disturbed when approached by humans, their natural rhythms thrown out of balance.

So the sprint is "locked", and Peter's pink button appears at the top of the global backlog, from where it flows into the next sprint.

On rare occasions a sprint is broken open, for example when Karen realizes that all of the end users will commit suicide if they don't have a pink heart-spawning button.

In such an event, Peter must make Bob happy (because Bob is crying that his blue button is delayed). And Peter must make the button team of devs happy.

This usually leads to a ritual involving chocolate or even hardware gift certificates to restore balance to the dev ecosystem.