A highly sought-after variant is the filled star error, where too much ink makes the star look solid, increasing its value to collectors due to the printing defect.
Tell you how to check if a star note is from a (using a Star Note Lookup tool).
While many star notes are actually quite common, they become highly collectible and valuable if they come from a low print run (under 3.2 million, or sometimes under 640,000 for extreme rarity), feature fancy serial numbers (like radars, ladders, or solids), or are part of older series currency.
Because they are not produced regularly, they are a "rare" treat to find in a standard bank teller strap of $1 bills.