The finale of Power Rangers in Space was probably the most memorable "entrance" I can remember. The hostaged crowd is told to give up the identities of the power rangers - or for them to step forward - and suddenly every single person claims to be a power ranger.
Jump to a scene of the real power rangers - out of costume - standing on a building in sight of the crowd and the villain. It's the first time the world sees the power rangers for the teenagers they are. As a kid, I remember how epic that entrance was, especially when they then suited up and proceeded to kick ass and save the crowd.
Eternity is infected with a case of cosmic consumption. Despite all his power, he can't heal himself. Mainframe asks who should he call for help? The Living Tribunal? The Celestials? NO! Eternity says ONLY one being has the power to save him!
Prime showing up in Solomon's ship and in Monarch's command ship are both great entrances specifically because of the expressions on their faces and his juvenile dialogue.
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“Where the longleaf pines are whispering
to him who loved them so.
Where the faint murmurs now dwindling
echo o’er tide and shore."
-A Grave Epitaph in Santa Rosa County, Florida; I wish I could remember the man's name.