After playing Twilight Princess and thinking about the Zelda timeline theory, I started to notice some similar things between Twilight Princess and the Link the Past. I will list the following....
OF COURSE THESE ARE SPOILERS FOR BOTH GAMES....
1. Zant brings Ganadorf back from the Twilight Realm to Hyrule in Twilight Princess. In a Link to the Past, an evil sorcerer named Agahnim that takes over Hyrule revives Ganondorf from the darkworld, but he doesn't complete his mission of bringing Ganadorf back to Hyrule (You kill ganadorf before it happens). However, I forgot if Agahnim came from the Dark World himself like how Zant lives in the Twilight Realm....
2. In Twilight Princess you think Zant is the main protagonist in the game. In a Link the Past you think Agahnim is the main antagonist as well.... You find out later, as you reach the fourth temple in both games, that Ganondorf is in the picture. In a Link to the Past, however, you learn about Ganondorf before you reach the fourth temple, but on the way to it.
3. In both games, you enter the alternative realm before you learn about Ganondorf. This reason is pretty weak, though, but hey, it's a similarity.
4. In both games, when you enter the alternative world, you change your form into animals. In a Link the Past, you turn into a bunny because you are a good hearted person, though, versus a heroic wolf.
5. In both games, residents in the althernative world change their forms. In Twilight Princess, they are souls. In a Link to the Past, they turn into creatures or objects that represent their personality.
6. You need to get an object in both games to retain your own physical form in the alternative realms. You can't switch back in a Link to the Past, however.
7. In both games, there's a mirror.... yeah... A Link to the Past's mirror is a handheld one, though.
8. In Twilight Princess, the guardians of light are captured in the alternative realm. Similar to a Link the Past, the sages, which represent light, are captured in the alternative realm.
9. In both games, Zant and Agahnim are puppets. You also beat them right before you kill Ganondorf. The realm you beat these puppets are also in the alternative realms...
That's all I can think of as of now. Of course, these reasons could be wishful thinking, but what do you think? Are these game really similar in your opinion? Discuss....
EDIT: I made a mistake for reason 8. The sages don't literally bring back light, but they do represent it. Also Agahnim is Ganondorf, forgot about that....