I was just about to do that
When someone says they were going to do something, but they're just trying to avoid being called out for not doing it, and it always ends up being a total lie
'I was just about to do that', said by the person who was still sleeping
'I was just about to do that', said while they were still scrolling on their phone
'I was just about to do that', said right after I did it for them again