By increasing the level of the Toad, there is a chance that the Toad will get a new improved external form. There are three such forms in total, and with each form the Toad becomes stronger (damage characteristics and hp in battle increase)

And it looks like this:

This is just one example.

Getting the form happens randomly as you increase a level:

• the second form is randomly from level 50 to 75 (the chance of getting 20% when getting a new level)
• third form randomly from 75 to infinity (chance of getting 2% when getting a new level)