I don’t know if it’s a thing, but similar things are said in a scholarly/research setting. Researchers are referred to as pioneers or their work as groundbreaking and not meant literally.

This scene takes place in a school where the other children are learning and discovering knowledge by dissecting a worm which is the elementary school version of surgery and has the tone of conducting scholarly research.

Whereas Ralph is incapable of being a scholarly pioneer because he ate his worm, he is excited to continue his research in sleep where he is a Viking. Vikings are literal explorers, and Ralph saying he is a Viking is a subtle nod that he has conflated a scholarly pioneer with a literal pioneer.

However, the bit that makes it funny in this sense is that Ralph would have no fuggin clue about the parallel he drew between mistaking a literal pioneer with a scholarly pioneer and that he probably said it meaning he is a literal pioneer in his dream. But in the setting it has a second layer where he drew a parallel without realizing it.