The Generic Seagull is...well, just that. He's a real-life seagull with no backstory whatsoever, so little is known about him. All that's known about him is that Brad Till once filmed him digging through a rubbish bag in Swansea. Perhaps he wanted some fish and chips.
The Generic Seagull appears in All Star Smashers as a Support Spirit, as a Novice class, where you must fight Edward Yui at Till Track to obtain him. When fighting Edward, he can jump 5 times in a row, get healed by traps, and will be distracted by items.