User blog comment:TheHandsomePlant/Modern Day Part 1 levels/@comment-24932254-20151224164916/@comment-5792287-20151224173751

For returning zombies, really only zombies that are going to be a threat should return, seeing as it's the last world. Football is pretty much confirmed by the code, but Pogo, Disco and Pole Vaulter I seriously doubt, due to Disco-trons and the various zombies capable of going over plants (most notably Jetpacks, Dodos and Bugs).

Zombies which I think are possible: Jacks (though MCs are similar, so maybe not).

Zombonis (we have crushing zombies, but nothing much like the Zomboni overall).

Diggers (since they are quite different to Prospectors, and while similar to zombies moved by Pteros, they aren't dinos).

Bungees (we haven't had a true Bungee yet, unless you count Parrots).

Ladders (the best of all disabling zombies ever, it has to return, though it may be buffed to the point of being pure evil).

Catapults (Plus Umbrella Leaf, which could counter certain other zombies too!).