Ms Lion Traditional Cache

Origin
Although he had no super powers or special abilities, Ms Lion believed that he could be a super hero.
He belonged to May Parker, but wasn't aware of his close connection to Spider-Man.
However, he did discover a super powered bouncing cat who called himself Hairball. Ms Lion was too enthusiastic to realize that Hairball didn't like dogs, and therefore Hairball didn't like Ms Lion either. Despite Hairball's vocal protests, Ms Lion continued to follow Hairball around hoping to help him fight crime.

Major Story Arcs
Pet Avengers:
Ms Lion was chasing Hairball around the park when Lockjaw and Throg appeared out of nowhere. Lockjaw had been teleporting around the city looking for other super-powered animals to help him collect the Infinity Gems before any super-villains found them. Hairball was delighted and accepted the invitation to join the team. Ms Lion was so excited and enthusiastic that he invited himself into the team, much to Hairball's displeasure.

Savage Land:
Once Lockjaw was satisfied that they had enough team members, he teleported them to the Savage Land. After they found an Infinity Gem they sensed that another one was also there but at a different time. So they used the power of the gems to travel back through time. In the past, Ms Lion's over-enthusiasm landed them in trouble. He bounded towards a nest filled with eggs and some of the Infinity Gems. However, the nest belonged to Devil Dinosaur who began to attack the team. Ms Lion continued to distract Devil Dinosaur with Zabu's help until the others had gathered the Infinity Gems from the nest.

Bo Obama:
The Pet Avengers' mission took them to the White House. There, they found the last of the Infinity Gems inserted on the collar of Bo Obama. Ms Lion was excited to see another puppy, but Bo had more energy then he did and soon ran away from the Pet Avengers hoping they would chase him. However, before the Pet Avengers could catch up to Bo, he was snatched away by Thanos.

The Ultimate Sacrifice:
The Pet Avengers assembled on the lawn in front of the White House. There, Hairball was about to attack Thanos. Thanos had already snatched the Power Gem from Bo's collar and was preparing to use it to attack Hairball. Ms Lion saw what was happening and dove into the line of fire. He saved Hairball from Thanos' attack, but was instantly killed.

True Friends:
Hairball was devastated by what had happened to Ms Lion, and in his rage he accidentally triggered the Infinity Gem he had been given. Power surged all around Hairball, and as he cried out the energy passed onto Ms Lion. Hairball had summoned the power of the Soul Gem, and brought Ms Lion back to life. He slowly woke up and hairball helped pull him safely away from the fight while the others bravely battled on.

However, Lockjaw didn't want to see any more of his new team-mates killed in battle. He took the Infinity Gems from the other Pet Avengers and looked as if he was going to present them to Thanos. However, he then teleported Thanos away from the others and began to battle him throughout the known universe. When Lockjaw returned to the others outside the White House, he had combined his teleportation powers with the energy of the Infinity Gems to trap Thanos in a pocket dimension.

Realizing that their adventure was over, Ms Lion grew sad. He didn't want it to mean the end of the Pet Avengers. So lockjaw used the Infinity Gems one last time to create a telepathic link between all of the Pet Avengers so they could call on one another in times of peril. Hairball was annoyed that he would have Ms Lion's thoughts in his head. Ms Lion grew confused, because he thought that Hairball was finally his friend. Hairball claimed he still didn't like dogs, but he obviously become friends with Ms Lion.

Dream World
In another adventure, Ms. Lion assisted the Pet Avengers in the Dream World. It's current magical ruler had become confused and angry, unintentionally causing mass hysteria throughout the land.

VS. Avengers
A further adventure brought the Pet Avengers in conflict with ancient dragons and the human Avengers. Eventually it was discovered the dragons were fighting to protect the young, who needed to gestate in the bowels of Earth then live in space after hatching. The Avengers, pet and human, soon recognized the baby dragons were innocent in this chaos and let them do what they needed. For the efforts in protecting the baby dragons, Ms. Lion and the Pet Avengers earned their own home-away-from-home on the grounds of the Avengers Mansion.

Powers and Skills:
None. Ms Lion is one of the few members of the Pet Avengers who doesn't have any super powers. Zabu and Redwing had strength and flight according to the natural gifts of their species, while Lockheed and Lockjaw had alien abilities. Throg was a human being mystically transformed into a frog, and Hairball shares the same telekinetic field that Speedball used to have.
Therefore, like Bo Obama, Ms Lion only had the natural energy and enthusiasm of a rambunctious young puppy.

Miscellaneous:
Ms Lion was originally an animated character in Spider-Man and His Amazing Friends. He was originally Firestar's pet dog, and lived with her, Spider-Man and Iceman. Although he no longer belongs to Firestar (who has a cat called Pumkin), Ms Lion still has a familial connection with Spider-Man.
There appears to be no reason for the female honorific in Ms Lion's name. The title of 'Ms' tends to be reserved for ladies, therefore it is unclear why he is not known as Master Lion. However, a strange and quirky name does seem to fit with his irrational and spontaneous personality.