Glitches happen when something happens in the game when it's not supposed to. Examples would be Catching a Moshling but it's not in your zoo or your monster is gone. These errors are usually fixed if you exit the place you are at, and go back to it.
Scrumpy has no owner.
The monsters are walking on Zack.
2 Katsumas
Tunies had the Techies house.
Gift in the Garden.
Same Date on all missions.
Sprocket and Hubbs at The Haunted Manor.