If guniea pigs start flying then my two will rise from the dead and start attacking my step brother. (Well thats what they did when they were alive.)

If hell freezes over we will have huge ques in the pharmacy of demons waiting to get cold and flu remedies.

OR

If hell freezes over Lucifer will open it up as a huge ice skating rink/theme park, with over priced gift shop where you can buy cute fluffy little satan and friends plushies.