I do have some balancing issues with some of the Magic Showtime monsters.
Ring Lady: upon death you could literally call upon ANY Light monster, and there are plenty of powerful Light monsters out there. Archlord Kristia and Splendid Venus, to name a few. Plus, it already calls out a monster upon summoning, and with no drawbacks on the summoned monster or itself, I might add.
Serenity Mermaid: with its effect, it can make its own ATK 2100, far too high for a mere level 4 monster to have without some sort of drawback. And that's not even considering other Magic Showtime monsters.
Magician of Light: its stats are too high. Level 4 2000 ATK monsters usually have low DEF or some drawback. This doesn't have either. Before you mention the direct hit thing, I don't think getting 1000 LP back is considered a drawback.
Magic Showtime Stage: too much of a buff for the Magic Showtime monsters, imo. Even the field spell Wetlands may grant a 1200 ATK bonus, but only for level 2 Water monsters.
XYZ Showtime Magician: too many effects for a mere rank 4 monster. Sending a monster to the grave upon summon, AND using effects for material detach? No. Also a nitpick here, "XYZ" refers to XYZ Dragon Cannon. You should have used "Xyz" as in an Xyz monster.
Bring Back The Act: I object to just summoning a destroyed monster back without drawbacks. In fact, it even gets a benefit of being unable to be destroyed by battle.
Begone None Believers: too OP. All it requires is a Magic Showtime monster. You can easily summon anything with that name and destroy 2 monsters with zero effort. Also, it should be "Nonbelievers," not "None Believers".
Dragonair Spirit: WAY too powerful. At a default 3000 ATK, it gains too much of a benefit from its effects. It is an even bigger beatstick than King of the Skull Servants, and that's saying a lot. Plus, you can't defend yourself with any effect when it attacks. Even Ancient Gear Golem isn't that strong. Plus, there is nothing stopping it from being summoned by means other than its own effect.