In one of the Gromble's Badass Teacher moments (This is from internal affairs, by the way), he punishes a parasite that invaded Oblina's stomach by sticking him inside a glass music box, perpetually twirling around. The parasite may not have been one of his students, but it had been toying with one of his students. So he felt he deserved something special.
The Gromble: BOOGIE OOGIE TILL YOU JUST CAN'T BOOGIE OOGIE NO MORE!
Ickis's growing abilities naturally provide him quite impressive feats (say, scaring other monsters or bears). In an episode where he befriends an old blind bluesman who lives in a building just about to be demolished, he saves the old man by growing so freaking HUGE that he utterly towers over the building and is able to catch a wrecking ball like a grape. Scaring off the entire deconstruction team was merely a little side effect this time.
The Gromble telling off the students for treating Ickis like a pariah because of his spontaneous combustibility. Even though he explained to them Ickis wasn't dangerous they still decided to listen to rumors.