After getting
you need to ...
*** Spoiler - click to reveal ***...get into green tentacle's room and get the videotape.
To get rid of nurse Edna occupying the surveillance equipment, you need Hoagie to get Ned and Jed switch places in the past.
*** Spoiler - click to reveal ***To do that, Hoagie has to go into the cellar to Red Edison, and get the left-handed hammer. Upstairs in Ned's and Jed's atelier, use the left-handed hammer when the right-handed hammer is resting on the barrel.
Push Edna out of the room.
Insert the videotape from green tentacle's room in the VCR and record Dr. Fred opening the safe. Make sure the switch on the right is set to SP.
If the IRS agents show up after Dr. Fred closed the safe again, you did it right.
Rewind the tape, and switch the right switch to EP. Play the tape to get the safe combination.
Go to the office, and open the safe yourself. If you haven't it already, get the Booboo-B-Gone from the desk drawer in the same room. Then take the contract from the safe and...
...use the Booboo-B-Gone on the contract to unlock the achievement.