In a 2010 interview with Yoshiaki Koizumi, producer of Super Mario Galaxy 2, he was asked by Japanese magazine Famitsu about how Yoshi can survive in space in the game. His answer was “because he’s a space Yoshi”. This is confirmed in the game as there is a special version of the sign in front of Yoshi’s house in Sky Station Galaxy, which can only be accessed during that galaxy’s third mission. Unlike the regular version of the sign, which contains a message signed “Yoshi”, this one is signed “Yoshi the space dragon”.
Main Blog | Twitter | Patreon | Store | Top source, bottom source: myself playing SMG2 on Wii emulator