The Museum
Poo is the final member to join your team and is a great addition. Unfortunately, his levels are very low right now and he could use some training to bring him up to speed. Take him to Dusty Dunes Desert and try out the Criminal Caterpillar trick for best effect. When you feel you are ready, head back to Summers.
Check out Poo's inventory and you'll notice a tiny ruby. Remember the museum in Summers? Take it there and show it to the guard to be allowed access to the back room. You'll encounter two Shattering Men inside this exhibit, so be careful and make sure you are healed up. These enemies are weak against PSI Freeze so you should be able to take them out quickly that way. You do not have to fight them if you can dodge them while walking around the exhibit.
Check the exhibit and you'll find out that Pokey went to Scaraba. The guard will give you a heiroglyph before you leave which you can put directly into Escargo Express. On the way out you'll get a call from the curator of the museum in Fourside. At this point, you have an option of where you want to go. You can either head back to Fourside's museum and continue on to Magnet Hill or you can go to Scaraba. It is recommended that you go back to Fourside as the enemies you encounter there are easier than those in Scaraba. With Poo still at fairly low levels, Fourside is a better choice. This guide will assume you have chosen Fourside.
 Magnet Hill
Before doing anything, make sure you have a lot of food items in your inventory. The next area you'll be going to has some very difficult monsters. It is also hard to get out once you've gone in, so make sure you have an Exit Mouse. If you need one, go to the house in Southern Onett where you found your first Exit Mouse in the game.
Go to the dinosaur museum in Fourside and pay to get inside. Talk to the curator guarding the back room and he'll ask you to get him an autograph from Venus, the new singer at the Topolla Theater. At the Theater, head backstage and talk to Venus. She'll gladly give you an autograph on a banana peel. Head back to the curator and give him the banana peel and you'll be let into the backroom where there is nothing but a manhole leading to the sewers. The only place to go is down. Make sure you heal and save at an inn first.
The enemies here are tough, so be prepared to heal when you need to. You can be possessed and it is difficult to get back to the hospital without using an Exit Mouse, so kill the ghosts you encounter as fast as possible to avoid this at all costs. It is recommended that you ignore all the doors and ladders on the way to the end of the sewers for now. After you defeat the boss here, it'll be easier to collect all the items.
Enter the dirty water by climbing down the ladder in front of you and follow it all the way to the far right. Do not climb out of the water, just keep going until you can go no more. When you reach the end, take the final ladder and you'll see a shiny spot in front of you. Talk to it to fight the Plague Rat of Doom!
After the boss battle you will be able to record the sound of Magnet Hill. Don't forget to grab the Carrot Key from the present. Head back into the sewers and into the water. Take the next ladder up and head through the door to find a Broken Bazooka, which Jeff will be able to fix into a Heavy Bazooka as soon as he has 45 IQ (just sleep at an inn). The Heavy Bazooka is an item (not a weapon) that Jeff can use multiple times to deal a ton of damage to multiple enemies. Continue to the left (you do not have to enter the water) and you'll come across another door which leads to a Magic Butterfly. You can grab it if you want. Go farther to the left and grab the Rust Promoter DX from the trash can. This item will deal a lot of damage to metallic enemies.
Go back until you find a ladder and enter the water again. Go to the left until you reach the next ladder and get out. Continue left and you'll reach a door that leads to a Broken Spray Can which Jeff can fix into a Defense Spray. This item only requires 1 IQ so you can do it as soon as you reach an inn. Go back down the nearby ladder and continue left some more. When you reach the next ladder, climb out of the water and go to the left. You'll find a Croissant. Go back to the right and into the room on the right of the ladder. Here you can grab a Broken Iron which Jeff will fix into a Slime Generator.
You have another choice of where you want to go here. You can either head to Dalaam and the Pink Cloud sanctuary or to Scaraba. Once again, it is recommended that you skip Scaraba for now and head to Dalaam. Pink Cloud is a relatively short area and the enemies are slightly easier.