Mars

Mars was first shown in Unfair Science Fair Redux (Another Story) when Candace steps into a Mars portal.

Candace
When Phineas says "Cool far away place", Candace doesn't know it means "Mars" until she steps through the portal. When she is on Mars, Phineas says "Welcome to Mars" and she gets mad at Phineas.

When a guy gets angry because he's been researching Mars only to see red rocks, the rover deactivates so Candace destroys it with her foot. But she doesn't realize that Martians are watching her.

One of the Martians alert the other Martians that Candace has destroyed the rover so that she gets recognition.

Phineas, Ferb, and Baljeet enter the portal from when future Baljeet, Phineas, and Ferb fixed it. Phineas asks Baljeet for 20 minutes to find Candace.

Candace is shown crowned queen of the Martians while Candace doesn't realize it. Candace gets excited and decides to play with her new Martian friends. But when Candace asks for music, the Martians are revealed to not know what music is. Candace sees that the Martians don't know music until Candace teaches them. Candace names the Martians "Good Stacy" and "Good Jenny". So the Martians want Candace to destroy the rover again.

Phineas and Ferb make Candace want to leave but mad at Phineas and Ferb, the Martians chase them.

Candace attempts to prove to Linda that she was crowned queen, but when Doofenshmirtz's first "-inator" shoots into Outer Space, Linda looks in the telescope but instead of Candace, it looks like a rhesus monkey wearing a powdered wig.

Doofenshmirtz
When Doofenshmirtz believes that the Martians will make him their king, they crown the baking soda volcano.