I was messing with frogs when I had noticed that they were going to eat the small slimes and magmacubes, even after I put them on the same team.
To repeat this, summon a frog and a small slime/magmacube and put them on the same team before the frog eats it. The frog will still go after and chase the slime/magmacube even though they are on the same team, unlike other mobs that de-aggro when they are put on the same team.
In the image, I had summoned a slime and magmacube with a high resistance level so they couldn't be eaten.
keep in mind the original code for both mobs regardless of the fact that they are on the same team. alongside skeletons and untamed wolves which exhibited the same behavior despite being on the same team. being on the same team only alters a small set of code. keep testing it and see if you may find anymore examples. Im curious.