Blake and Ruby are teammates who met during their first night at Beacon. Later on the two were assigned to a team together alongside Yang and Weiss. A few episodes later the two of them met Penny on the side of a street after Weiss knocked the other girl down. Ruby and Penny became fast friends while Blake and Penny took a little bit longer.
When Blake was missing Ruby and Penny searched throughout the city for Blake. When they find her Blake is fighting Roman. Penny and Ruby join the fight to help her. The three sit down and talk at the end of the fight against Roman. Penny disappears when a car arrives to pick her up. While Penny returns in volumes 2 and 3 she spends most of her time with Ruby and not Ruby and Blake. Blake and Ruby both react to Penny's death in volume 3, upset.
Penny returns in volume 7 having been rebuilt by her father. She helps teams RWBY and JNR, Oscar, Qrow, and Maria fight off grimm after they met her father Pietro. Blake and Ruby were happy to see Penny alive and well again. Penny had to leave to protect the city but reunited with the two and the others again later when they were being take to Ironwood. Penny's happy to see everyone again and after their meeting with Ironwood takes them to their room. Penny is also seen waking Ruby and Blake up alongside their teammates after their first night sleeping in the dorms. She is also excited for Ruby and Blake to get their huntresses licenses from Ironwood and celebrates with them.
In volume 8 Ruby, Penny, and Blake go on a mission with Nora, Weiss, and May. They all fight the ace-ops together. After the mission Penny says goodbye before leaving to meet up with her father. When she crashes injured, Ruby and Blake are clearly concerned. When the virus within Penny starts acting up the two work with everyone else to try and keep Penny from flying off to retrieve the Relic of Creation and self destruct. Ruby and Blake also go along with Penny to retrieve the relic and use it to remove the robot parts from penny, leaving her a human. She then in turn hugs both of them, one at a time.
As Ruby's plan to evacuate Atlas and Mantle is underway, they are attacked by Cinder. Cinder tries to knock Ruby off the bridges, but Penny throws Blake, who catches her. Blake uses her weapon, Gambol Shroud, to try and save herself and Ruby. Cinder cuts her weapon leaving the two to fall. Ruby and Blake fall together into the darkness under the bridges and Penny is extremely upset at this, crying out, and shedding tears.
As of right now they are not aware of the fact that Penny died after their fall.
Mechabug is a rare pair ship within the RWBY fandom. The pairing doesn't have much art, but a few edits of it on. As of right now there isn't any fic of this pairing on Ao3 and the ship tag for these three characters has not been used enough to be official on that website though a variation of the tag including Weiss Schnee is with these three is.
- Nuts and Dolts refers to the ship between Ruby and Penny
- Ladybug refers to the ship between Blake and Ruby
- Double Bow refers to the ship between Penny and Blake
- Winter Greenhouse refers to the ship between Penny, Blake, Ruby, Weiss Schnee and Nora Valkyrie
- "Mechabug" comes from a combination of the previously existing ship, Ladybug, for Ruby/Blake, adding Mech in front of it to represent Penny.