The first appearance of zombies in fiction is quite a mystery. Different scholars have different opinions. Some think it started in certain ancient cultures' tales, while others suggest it was in more modern works. But no clear consensus exists.
Batgirl first showed up in Detective Comics #359 back in 1967. This was a significant moment in the comic world, introducing a popular character that has since had many storylines and developments.
The Joker first appeared in Batman comics in 1940. It was a significant moment that shaped the Batman universe.
The Scarlet Witch made her first comic appearance in 'X-Men' #4 in 1964.
Loki made his first comic appearance in Journey into Mystery #85 back in 1962.
Ultron made its debut in The Avengers #54 back in 1968. This was a significant moment in comic history as it introduced this powerful and menacing villain.
The first time Batman and the Penguin showed up together in a comic was in the 1940s. It was a significant moment that set the stage for their ongoing rivalry. Over the years, their interactions have evolved and kept fans engaged.
Starlord first showed up in comics back in 1976. This was a significant moment for the character and marked the beginning of his story in the comic universe.
Deathstroke's first comic came out in 1980 in 'The New Teen Titans' #2. It was a significant moment for the character's introduction to the comic world.
The first appearance of Batgirl in Detective Comics was in 1967.
I have no idea when that was. You might have better luck checking with comic book publishers or dedicated comic history websites.