Flushback appears in the Seaside Cave (San Fantastico).
Befriended (Yo-kai Watch 2): "Now I remember! I wanted to be friends with you!"
Befriended (Yo-kai Watch: Wibble Wobble): "Ah, now I remember! I wanted to be friends with you!"
Receiving food (favourite):
Receiving food (normal): "Nothing Special."
Receiving food (disliked):
Flushback first appeared in EP090 where he started out as an ordinary turtle who was traumatized from an incident where he was almost flushed down the toilet only to be saved by his owner, a little girl, using a plunger. As such when he becomes Flushback, he makes people he inspirits remember their past traumas. He first appeared where he inspirits Nate when he tries to do his class duties to impress Katie. In a bid to "forget" his past trauma, he summons Dummkap who manages to make Flushback forget his own past trauma. Unfortunately, this made both Nate and Flushback embarrassing idiots as a result and costing Nate a chance to be partners with Katie on a project.
Omoidasuppon might be based on the suppon no yuurei (ghost of the soft-shelled turtle), a youkai that once haunted a man who regularly feasted on soft-shelled turtle meat, which was once believed to have curative properties, and cursed him with uncontrollable shivers. Just like a turtle doesn't let go once it bites into its prey, this creature is very persistent in its haunting.
"Omoidasuppon" is a portmanteau of omoidasu (to remember/recall) and suppon (soft-shelled turtle).
"Flushback" is a portmanteau of flush, flashback, and leather-back turtle, a soft-shelled turtle.
"Desolvidador" is corruption of desolvidar (unforget) to make it sound like desatascador (plunger).
"Yvantouse" is a portmanteau of "Yvan" (a french name) and "ventouse" (plunger).