The film asserts that you can only spell two words with the letters "R-O-O-M-N": "moon" and "room." At least 10 words of between two and five letters can be made from those letters, including "moron".
The narrator asserts that Kubrick changed the two Grady sisters into twins as a reference to the NASA Gemini project. However, Ullman clearly explains to Jack earlier in the film that the two girls were aged about 8 and 10. Therefore they were not twins.