His catch phrase is "I am that hero"!, but it was in different phases
In the beginning he said "Danger lurks in the big city, disaster wait in every dark alley, peril behind every dark bench, the world needs a hero, but not just an ordinary hero no, a special hero, a superhero I AM THAT HERE THEY CALL ME LARRY-BOY, wherever there is trouble I'll be their, whatever a helpless vegetable calls out I'll answer, evildoers beware you are no match for the awesome power of LarryBoy and his super suction ears." Then at the end he says "The world needs a hero I AM THAT HERO they call me LarryBoy.
He says his catch phrase in his theme song.
He says "OK, I can do this, I am after all, a superhero."
He says when at the end of his intro theme song, when he comes to action (except in The Good, The Bad, and The Eggly!, but he does say it in the episode).
He says it in his fourth theme song Rock On, LarryBoy. In the beggining he says "Remember kids with great chocolate comes great responsibility."
He says it in the Bumblyburg Science Museum, and when in the battle but he gets scared.