A hazel-green clam shell with a zipper poking out of the right of it's mouth. It has a long dark pink tongue and is shown holding a 500 yen coin with three gold coins floating around the top of it. Inside of the shell is a golden eye.
Loves to be wasteful, he believes that spending money boosts the economy through "trickle-down economics" and that greed is good. In the English version, according to the Yo-Kai Wiki, Spenp comes from the 1980's.
Once Spenp inspirits someone, they'll be compelled to splurge on things they don't even particularly want.
Spenp first appears in EP011, in which causes a streak of money wastes by Nate and his friends of the money they saved to buy a manga magazine (though in the English version, it was a video game). When confronted by Nate, he bluntly states it is fun to waste money and when asked by Nate about it, he counters asking if the economy would super-recover if no one is wasteful. After Nate and his friend win the manga magazine issue in a lottery, Spenp gives Nate his Yo-kai Medal. Nate states he wouldn't summon Spenp much.
Despite the above statement, Spenp is first summoned in EP072 to deal with Greesel. He quickly becomes friends with the elder Yo-kai and invites him for eating.