Rocket boot
From Jenny Everywhere Wiki
A rocket boot, originally one of a pair, was one of the items accumulated in the closet of Jenny's apartment in one universe. When she and Kim went through the closet to sort its contents, they found it again and decided to set it aside to give it to Professor Awesome so long as his mother allowed it. Jenny apparently had a long and whimsical story about how she'd acquired the boot, but Kim didn't want to hear it. (PROSE: Cleaning Day)