The blimp seen in Lungfishopolis is a possible reference to Grim Fandango, where a blimp suspended above a bridge is prominently visible whilst exploring part of Rubacava. Just like Razputin in Psychonauts, Manny Calavera in Grim Fandango says the words "There it is..." whilst in this area.
, in Grim Fandango Manny is in fact referring to the large cat racing track when he says this which is just visible towards the right of the screenshot. Despite this, there is still a strong chance that it is a reference as Tim Schafer was also responsible for Grim Fandango.
Thanks to Tingler for this reference and the screenshots!