You never need Frog or Lucca for any mandatory fights (unless you're playing the DS/iOS version where you need Lucca in a boss fight) just swap them for the event they're needed in. Robo is mandatory for a dungeon, Marle is mandatory for a boss fight. Ayla doesn't have anything to do and is just along for the ride.
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http://i43.photobucket.com/albums/e373/Gaiash/KumaVsZangief.jpg
LOL!!!! I hope that's a joke....names don't get more n00bish than that