Diane was B.O.B.'s gelatin girlfriend.
After being released from Area Fifty-Something following the defeat of the Robot Probe Susan Murphy's parents Carl Murphy and Wendy Murphy threw their daughter a welcome home party. While at the party B.O.B. met a inanimate blob of gelatin which he subsequently dubbed Diane. Though B.O.B. at first believe "she" gave him a fake number the two later reunited and B.O.B. would take her home as his girlfriend.
After The Missing Link accidentally ate the blob of Jelly Susan and Dr. Cockroach set out to make a new one so to spare B.O.B.s feelings. After many setbacks thank's to Dr. Cockroach's mad science "shortcuts" the two monsters finally made a replacement Diane only for B.O.B. to break up with it revealing that he met a banana pudding cup and fell in love with "her" followed by Coverton eating the gelatin.