The following “Limited Edition” Kellogg’s cereals do NOT bear a K or an O/U symbol and are NOT certified Kosher, due to the addition of marshmallow (from non-Kosher gelatin)…
Apple Jacks with Spooky Marshmallows
Chocolate Frosted Flakes with Spooky Marshmallows
Froot Loops with Spooky Marshmallows.
Other Kellog’s cereals that contain marshmallows or gelatin are also not certified. This includes Frosted Mini-Wheats (all varieties), Rice Krispies Treats cereal and some others.
Those Kellogg’s cereals that are Kosher bear an O/U or O/UD (dairy) symbol on newer packages. Older packages that bear a “K” or “KD” are also O/U approved, except for Kellogg’s Mini-Wheats Unfrosted Cereal, which is not O/U approved even when the package bears a “K”.