It looks much like the normal SpongeBob, except that it is made from a bubble and is completely transparent/pink. It has a shiny glow to it much like the other bubbles shown and appears to be the same height as SpongeBob.
It misses some of the specific details of SpongeBob, in particular his pants, his shirt, and the holes on his body.
It had the some role as the episode, After SpongeBob and Patrick blow versions of themselves in Jellyfish Fields after a flashback has happened.
SpongeBob tries to replace Squidward and blows this bubble in order for him to make the scene of Squidward playing his clarinet. SpongeBob then yells at Bubble SpongeBob, while pretending to be Squidward, for interrupting his clarinet playing.
SpongeBob Comics No. 22
He is seen on the cover and in the comic strip Bubble Double Trouble.
The SpongeBob Movie: Sponge Out of Water: The Junior Novelization
He had the some role as the film.
The SpongeBob Movie: Sponge Out of Water
SpongeBob is seen blowing bubble versions of himself, Patrick, Gary, and Squidward into the sky.
SpongeBob Comics: Book 3: Tales from the Haunted Pineapple
Him and Bubble Patrick were seen in the Bubble Double Trouble. segment of the book, where he has the same role he has in the comic.