When you summon a frog and do the command "/data merge entity @e[type=frog,sort=nearest,limit=1] {NoAI:1}" the frog will loose it's ability to move, but the animation still stays when you punch it.

This will not work by summoning the frog with the NBT with "/summon frog ~ ~ ~ {NoAI:1}". The frog must be summoned with AI for this to work.

Here's a video I made on this
https://www.youtube.com/watch?v=SbhoPXV4-CU