Not a problem at all! Helps me put some rhyme to the reasonless slaughter that just occurred on screen, too.
The characters only act out as much as you make them do. So if all one needs is 2 seconds of backup, you play that, press "B" to Time out, and then do it again on that spot. If you want them to run 60 seconds of stage and then rewind, and fight along side them, that's ALSO an option! Each clone will act out the total actions you played. After that, they disappear.
There's some unique wrinkles to that, but hopefully, you just naturally catch on to them as you play.
People you timeout yourself just disappear, I believe. This takes one of your 30 lives. The ones that are killed pop a little skull bubble up on screen, showing where they died. If you save them, then they float in space, waiting to be rescued and become a power up. I think this still counts as a lost life, too.
The powerup adds their charge attack to yours. So you can actually have Shieldy shooting Aimy's sniper shots while dropping a shield, or a Aimy sniper rifle that shoots Mel's Shotgun shells simultaneously...
So basically each spawned character counts as a resource. Either one that gave you assistance, and disappears, or one that can be saved from death, and absorbed to give you extra firepower and HP.
The Glorbs in the stages each give you an additional life, so you don't have to worry TOO MUCH about spending lives for profit, initially.
It's satisfying to me, that in a game that allows you to have SO MUCH firepower... one properly used character still feels like they can wreck shop. I think I fell in love with Melanie Gibson and her shotgfun at first use. She actually did REAL damage, much like Aimy's charges.
I also love how watching the replays can make you look like the BEST PLAYER EVER, haha. All you see is a straight run, with you killing enemies before they have a chance to fire, deftly maneuvering through obstacles, and grabbing each secret, without any stop in progress.
It's almost like every stage is your very own Tool-Assisted Superplay!