This is how Our Heroes went to the Adventure Time World and how they bring Mordecai and Rigby home in Weekenders Adventures of LEGO Dimensions.
They made out of the Portal and they saw Finn, Jake, Mordecai and Rigby running from something
Mordecai: Talk Later! Run now!
Dora Kid: What's with him?
They saw a Giant Cake Monster and they are running away from it and they hide from it
Finn: And it's going to eat us!
Tino: How did it happen?
Mordecai: Well, you see this.
Flashback has Started
Rigby and Jake are watching a Monster Movie
Scientist: Soon, Igor, it will be time, soon the lighting will commence. Soon I shall bring my creation to life!
Rigby: Soon, I'll get my sandwich to watch this.
Finn and Mordecai making a Cake for Jake's Birthday
Finn: Here's the frosting I'll need later, and I have my cake decorations.
Mordecai: Look it's starting.
They have to follow the ingredients from Princess Bubblegum on TV
Princess Bubblegum: Now, if you all ready, we'll start, okay? Now to make our cake fluffy and yummy, add in a whole cups of baking soda.
Finn & Mordecai: One whole cups of Baking Soda.
Princess Bubblegum: Three Dashes of Vanilla.
Mordecai & Finn: Three Dashes of Vanilla.
Princess Bubblegum: Half of cup of sugar.
Mordecai & Finn: Half a cup of-
They realised they forgot the Sugar
Mordecai: Oh no, we forgot the Sugar!
Finn: Rigby, quick! You keep adding the Ingredients like she says while we ran to get one.
He and Mordecai left
Princess Bubblegum: Now the next thing we need to add is a cup of flour.
Rigby: Mordecai and Finn didn't make this one so big. So put them all.
He put all the Flour
Princess Bubblegum: 2 sticks of Yeast.
Rigby: Twelve sticks of Yeast.
He put them
Princess Bubblegum: Add a cup of Milk.
Rigby: (in Garfield's voice) All the Milk.
Princess Bubblegum: Add in the few piece of Chocolate.
Rigby: All of the chocolate we have in the house.
Then Mordecai and Finn came back with the Sugar
Mordecai: Thanks, Rigby. Me and Finn will take over.
Rigby: Yeah. Cooking is more fun with other heroes.
He leave with the Sandwich
Finn: Ok. Where were we?
The sugar bag lands on the remote
Scientist: 2 cups of vinegar.
Mordecai: 2 cups of vinegar?!
Finn: Well. I guess she knows what she is doing, Mordecai.
Scientist: Sodium Carbonate and Sulfur.
Finn: Sodium Carbonate and Sulfur?
Mordecai: Where can we find? Oh, that's right! My old Chemistry Set!
They went off to get Mordecai Chemistry Set, and they put it on the bowl
Scientist: Add in the Ammonium Chloride.
Finn: Ammonium Chloride?
Mordecai: This is weird.
Scientist: Now, it is time to....
The TV Switch programs
Princess Bubblegum: Put the batter in the pan and put it in the oven.
Mordecai: I hope Jake like this cake.
They put it in the oven and they watch the Monster Movie with Rigby and Jake
Scientist: The power of the lightning will bring life to my creation.
Then lightning happened and it make Jake the dog Scared
Scientist: Even now, the power of lightning is working.
Finn: Calm down, Jake. It's just a Storm.
Jake: I'm Scared!
Finn: Jake, you're acting like you're in that silly monster movie.
Scientist: My creation is begining to grow. It is coming to life!
Rigby smell that cake in the Kitchen
Rigby: I'll go have a small piece. About the size of Cybertron.
The Kitchen is dark, he turn on and nothing's working
Rigby: Oh man. Lights are out. But, like Garfield, I can find my way to food in the dark.
He saw the Cake in the oven gone
Rigby: Huh? Where is the cake? [Looks at the camera] Did you steal Jake's birthday cake? That's Garfield's thing. Admit it. You took Jake's cake. Well, it didn't just get up and walk out?
Then he touch something and he saw a Cake Monster
Rigby: It's amazing. It's awesome. It is an great size for pudding.
Cake Monster is gonna eat him
Rigby: What did I do to you exept me and Ryan eat a lot of your buddies?
He grab the Frosting
Rigby: Ok, Cake. You asked for it.
Mordecai heard the noise coming from the Kitchen
Back to Rigby
He spray the Frosting to the Cake Monster and fire Cake Decorations
Rigby: Now that's what I call a cake.
Rigby: But it's still a monster!
Finn: Did you try to eat the cake we made?
They turn on the light and saw the Cake Monster
Rigby: For real, guys. It's the other way around!
Mordercai & Finn: It's- It's- It's-
Rigby: Yeah, it's one of those. Follow the Raccoon!
They are running away from it
Flashback has ended
Tino: And that's why you run away from that thing?
Mordecai: Yeah. And we have to run!
They saw the Cake Monster again, so they run away from it
Finn: Run! It's cake-zilla! And I don't know how this happened!
Mordecai: We did what Princess Bubblegum does.
Tino: Then maybe she'll know what to do!
Then the stop because of the Stoplight, they are taking a breath after running, and then light goes Green, they continue running
Princess Bubblegum: And we'll be back to see how Our yummy cake turned out right after this commercial.
Man: And we're out. Back on the air in 30 second.
Princess Bubblegum: Lumpy, how do you enjoy the show?
Lumpy: The show's boring. Who wants people to cook?
Princess Bubblegum: But I was trying to make it interesting. Yesterday, I made veal scallopini. It was wonderful!
Lumpy: Veal Scallopini is boring, too. That's why I'm cancelling your Program.
Princess Bubblegum: Oh, please, don't cancel me, Lumpy. Cooking is my life!
Lumpy: After you finish today's show, take your spatula and get out.
Man Back from the commercial in 10 seconds.
Bad Cop got separated from the Others
Bad Cop: Guys? Dora Kid?
He saw them and he began to chase from the Cake Monster
Rigby: This way.
They went to the castle and the Cake Monster is climbing
Princess Bubblegum: Now let's see the oven and see how our- our cake turned out.
Then a Cake Monster has appeared
Princess Bubblegum: I knew I put in too much baking soda.
Then Our Heroes has arrived
Mordecai: Somebody has to stop it.
Rigby: And I'm afraid someone is gonna be me, it won't be pretty, but I have to make supreme sacrifice. I'm gonna eat it!
He's gonna eat it
Rigby: Hey, could I get about 500 gallons of Ice Cream to go with it?
Then he got off the Cake Monster
Rigby: Wait, stop! I was just kidding about eating you! I'm on a low cake Diet!
He went outside and he has to be careful and then Cake Monster grab him
Mordecai: My best friend! Where are they going?
Princess Bubblegum: He's climbing the Tower!
Tino: This is awful!
Princess Bubblegum: This is Terrible!
Lumpy: This is beautiful! This is what your show needed, I'm giving you another season.
Princess Bubblegum: Wow! Thank you!
Back to Rigby
Rigby: I know what to do. Hey, Bakery boy, look at me for a second.
He give him a spoon
Rigby: I think I'd better get off this tower in a hurry.
He got off the Tower and then Cake Monster has been destroyed by Lightning
Mordecai: Rigby! You did it!
Princess Bubblegum: We seen the last of that horrible monster!
Then a Cupcake fall onto him
Rigby: I'd say about the next ten minutes, it's gonna be raining cupcakes. Happy birthday, Jake.
Jake: Thanks. I did like this better.
After that, our heroes take Mordecai and Rigby Home and went to another dimension