Baby Luigi (also called Billy in R64: Mario Goes Shopping) is a minor character in the SMG4 series.
He is the baby form of Luigi.
He later appeared in R64: Mario Goes Shopping, where X calls him Billy, saying to him that he can't play in the street. Mario then runs over X, prompting Baby Luigi to say "Dafuq?". Later, X crawls back to warn him not to play in the street, only to be hit by Mario's car again. Baby Luigi responds "Surprise, motherfucker."
The next time that he appeared was in The (TOTALLY ACCURATE) Documentary of Mario where he meets his brother, Baby Mario in an orphan.
In SM64: Meet the Luigi, he was taken by a vulture and got scared.
- In "How Mario was born" SMG4 says that Baby Mario is his mother, but in the "(TOTALLY ACCURATE) documentary of Mario" it is stated that he met him as an orphan.
- X warned him to not to go on the street (Despite X being evil).
- In SMG4: AREA 64, Baby Luigi himself doesn't appear though an evil look-alike called BabyLuigiOnFire appears as a cameo.