This is how our Heroes arrived in Phineas and Ferb's World and how they save Dimensions from Doofensmirtz in Ryan's Quest.
[They arrived in Danville and they saw Phineas and Ferb surrounded by Heartless]
Phineas: Help us!
Ryan: We'll stop them.
They are fighting them and they defeated them
Ryan: How you like that?
Phineas: Wow, you help us. Thanks.
Ryan: Yeah, and you have to make sure that you and your brother is safe from those Heartless.
Phineas: Heartless? Those creatures you fought? I never seen one in Danville.
Phineas: This is where me and Ferb lives.
Evil Ryan: Does Ferb talk?
Phineas: I don't know, if he could.
Ryan: Oh, okay. Do you have a Pet?
Phineas: Yes. His name is Perry.
Ryan: Hey. Where's Perry?
Phineas: He's on a Mission to stop Doofensmirtz.
Phineas: I could help him, but there are troubles in Danville.
[They saw many Heartless and it's coming from Doofensmirtz Evil Incorporated]
Singers: Doofensmirtz Evil Incorporated~
Ryan: Whoa, there's a lot of Heartless here.
Phineas: And I need to stop Doofensmirtz!
Ryan: Can we help you?
Phineas: Okay! Follow me!
They went off to Doofensmirtz Evil Incorporated and they look so tired for climbing up the Stairs
Ryan: We're coming. Oh man. It's like last time in the Octan Tower!.
Doofensmirtz: This is it! Perry the platypus, the Tri-state area will be taken over!
Then our Heroes has arrived Exhausted
Evil Ryan: Stop right there.... you Pharmacist.
Doofensmirtz: Are you serious about me being a Pharmacist? And aren't you a little young to save the world?
Sci-Ryan: Yeah.... Yes we are.
Ryan: (Panting) Can someone give us some water?
Doofensmirtz: Sparkling or Regular?
Doofensmirtz: Psyche! (laugh)
Ryan: [gasps] You really are a bad man in the entire Tri-State Area. Prepare to be defeated!
Doofensmirtz: Bring it on, techno-organic kid.
He brings his Heartless
Doofensmirtz: Bring it on!
They are fighting him and they defeated him
Ryan: Fore! [swings his Keyblade and sends Doofensmirtz flying]
Doofensmirtz: Curse you, Ryan the Techo-organic boy!
Ryan: Time to shut it down.
They shut down the Machine that summon the Heartless and they saw a Keyhole, Ryan sealed it
Ryan: Time for us to leave.
Phineas: We'll miss you.
Ryan: Do you think we'll come back?
Phineas: Yeah, you can come back anytime.
Ryan: Okay, bye!
Ferb: See you later, Ryan. [notice Perry] Oh. There you are, Perry.
They left this world