1000 pull-ups in a week. The idea seems impossible till you break it down into small parts.
ie. 10 pull-ups every 30 minutes for 10 hours for 5 days.
Or slightly easier, 2 sets of 12 squats, 3 times a day for 7 days, is over 500 reps.
You just needs discipline, a plan and to start the first exercise. After 2-weeks it will be a new healthy habit.
Much is the case of learning a new language, you can listen to 30 minute episodes during your dead time like a commute. After a few months you should be conversationally ready.
The key is to keep challenging yourself, ensure you have accountability and a carrot or stick at the end.
Try it!