I think my favourite picks for NASB guests (not counting - and assuming we already have - Nickelodeon characters with licensing issues like Timmy) are Danger Mouse (Nickelodeon's first cartoon icon, so popular for the channel pre-Nicktoons they had to do a promo announcing his exit when they lost the rights) and Heathcliff (Garfield rivalry, aired on Nickelodeon) - unlike a Dreamworks character, I can't imagine these two being that hard gets, both's shows are on Paramount+, and both have really good moveset potential (though in the case of Heathcliff I think the moveset would have to lean more in the direction of modern Dada Heathcliff than classic Heathcliff - I definitely wouldn't consider Heathcliff if Garfield weren't in the game though.)