Tentacular Circus, like many Turquoise October songs, is an electronic song, featuring many chiptune influences and unorthodox production. It appears to contain various unusual samples of vocals, whistles, bells and trumpets. It is heard in the Octo Valley missions Gusher Gauntlet, Inkrail Skyscape, Tumbling Splatforms, Pinwheel Power Plant, and can also be heard in Squid Beatz.
Tentacular Circus (Splatoon Single Player Trailer)
Tentacular Circus was first heard in the reveal trailer for Splatoon's Hero Mode. It starts playing about 37 seconds in, after a short Cephaloparade remix. Unlike other versions, it has a proper ending, consisting of a modified version of the beginning.
Tentacular Circus (Kettle)
This version of the song is simply the beat played from 0:02 to 0:04, but muffled and echoey, making it sound like it's being played from a distance. It plays when the camera is near a kettle containing a level with the main track.
Tentacular Circus is based on a portmanteau of 'tentacle' and 'spectacular'.