Belligerent of the Ball/Lord Skitter not Triggering
Having Belligerent of the Ball and other creatures on the battlefield, next turn I played Lord Skitter, who triggers at begin of attack step creating a 1/1/ token, but this doesn't trigger Belligerent of the Ball.
[Deleted User] commented
Belligerent of the Ball's trigger has an intervening-if clause, which means it must be true when the trigger would go off, or it doesn't. At the beginning of combat only one nonland permanent has entered so far, so no trigger. Your rat token was simply too late.