Squid Doodle is a picture drawn by Patrick in the Season 2 episodeFrankendoodle.
The Squid Doodle
When Patrick drew the doodle on the ground, SpongeBob thought it was another Jellyfish, as he drew one earlier, but Patrick said it was Squidward.
SpongeBob: Hey, another Jellyfish!
Patrick: It's Squidward, silly!
It soon came to life, and SpongeBob insisted Patrick erase it because they could not let it roam around the town, so Patrick erased the Squid Doodle, then saying "Poor Squidward."
Spongebob Universe
Squid Doodle is a Spongebob's enemy[durable to Squidward],and,he is a member of Doodle Spongebob Killers.