Sure. Except, Noob's first appearance was as a secret boss fight and Ermac's as a hidden playable character. Rain was never meant to become a real character (I'm pretty sure Boon has actually explicitly said this before) and only ever got lucky to be added to the home versions of UMK3 and MKT.
From the wiki:
"A huge fan of Prince, Boon's inspiration for the character was the 1984 track P
urple Rain, coupled with his jokingly wondering what color palette had not yet been used in the games. In another nod to the singer, Rain addresses himself as "Prince of Edenia" in
Mortal Kombat: Armageddon. By the time Boon had decided to include him as a selectable in
UMK3, the game was already completed, so due to time constraints he had to hack into the attract mode to insert a snippet of the character as an unplayable red herring who was a purple palette swap of Scorpion, while creating a new font for displaying his name in his power bar; therefore, it is the only one in the game that is not italicized.
Rain was made a playable character with his own backstory and distinct set of moves for the home versions of
UMK3 and the 1996 home-release compilation title
Mortal Kombat Trilogy."
His first appearance was a tease(HA) but he was always meant to be playable, they just didnt get him into the arcade version in time. A normal thing to happen in MK games. Tremor was suppose to be in Trilogy also but was axed.
If he was never meant to be a real character, he wouldnt have been made a character at all.