Searching specifically for problems with Smash Bros for 3DS, I found a variety of posts by people also suffering this problem with this exact game, largely from GameFAQs, Reddit, GBATemp, and just all sorts of different websites with differing values of useful information
Otter is a Common, Token Creature - Otter card from the Magic The Gathering set Bloomburrow Tokens (MTGSC-TBLB-0025)
Fuse (You may cast one or both halves of this card from your hand.) Illustrated by John Di Giovanni Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
However, I decided to take things a step further, and figure out what deck should I have played, hypothetically, if I knew exactly what my opponents would play. The deck I came up with was
Type: Psychic
Ranked #6 in the set, trading at roughly 5% of the top card's price