Lil' Lightning is a light orange Pembroke Welsh Corgi with creamy peach fur and cream-colored paws.
He wears a blue leather collar with a license of a yellow lightning bolt.
At first, Lightning is a trusted ally and very sweet and loyal. He has always loved Thunderbolt and looked up to him as a brother-like figure.
However, he eventually became bitter toward Thunderbolt for acting selfish, disrespectful, and rude toward him and having had to tolerate it for a long time, as well as jealous of his fame and attention from ladies. He later planned to get rid of Thunderbolt so he could take his place on the show. This is when he began to develop a scheming mind behind his kindness.
Even though he plotted against him, Lightning still does show a bit of remorse and genuine feeling when Thunderbolt fakes his death towards the climax of the film.
Overall, Lightning is not in any way a bad dog; he was just overcome with jealousy at Thunderbolt getting more attention and admiration than himself.
Lil' Lightning starts off as the loyal sidekick of Thunderbolt in The Thunderbolt Adventure Hour. When Thunderbolt makes a special appearance in London, Lil' Lightning appears when the director announces his cue. Three lady dogs appear and swoon, making Lightning think they are calling for him. He approaches, greeting them and politely saying it is nice to meet them. However, the ladies revolt, harshly rejecting Lightning and praising Thunderbolt. Thunderbolt tells Lightning the ladies are not interested in sidekicks, but rather the hero. This makes Lightning sulk in sadness and humiliation while Thunderbolt is enamored by the ladies.
Later, Lightning runs into Thunderbolt's trailer, frantically telling him he overheard what the executives are planning for the next episode, which he says something horrible is going to happen. Lightning reveals that what happens in the episode is that Thunderbolt dies. Initally shocked, Thunderbolt begins to take a liking to it, stating he has always wanted a death scene. He asks Lightning how he will make his shocking return, to which Lightning responds he does not since he will remain dead and never return, not even for a reunion show or a cameo in the remake. Thunderbolt is shocked by this as he realizes this means the executives are writing him out of the show. Lightning says they are going to replace Thunderbolt with a younger dog. Thunderbolt freaks out, telling Lightning he has to help him so he will not end up on the street. Lightning suggests Thunderbolt do something heroic in the real world to get his name in the papers.
Afterwards, the director is worried about Thunderbolt missing, but finds a picture of Lightning, so he decides to re-write the show slanted towards him. Lightning peers through the window and chuckles, saying this is a whole new direction, revealing he has tricked the director. He then taunts a Thunderbolt plush, asking what he thinks of it. He declares he will finally be able to step out of his shadow as he has become tired of it, as well as being mistreated and shunned. After pushing the plush down to the floor, Lightning calls Thunderbolt an "overrated, overacting ham" and jumps down next to the plush. Lightning proclaims the show as The Lil' Lightning Adventure Hour, saying it has a nice ring and mockingly asks the Thunderbolt plush what he thinks and then chuckles sinisterly.
That night, when news of Thunderbolt and Patch planning to rescue 98 Dalmatian puppies from Cruella De Vil reaches Lightning, he realizes the deed will endanger his chance at fame. He worries that if Thunderbolt gets lucky and succeeds and the press got wind of it, he would never be rid of him.
Lightning reaches Patch and Thunderbolt at Cruella's hideout, telling him he came as soon as he heard. He joins the two on their mission as they spy on Jasper and Horace. Patch suggests to Thunderbolt to use a stealth plan. But Lightning tells Patch it will not be necessary as they could openly attack instead. This results in Patch and Thunderbolt getting locked up along with the other puppies.
When Patch tells Thunderbolt he knew he was faking, Lightning reveals himself, confirming Patch's claims. When Thunderbolt happily calls him, Lightning declares to him that he is not his "little buddy". He also reveals to Patch that Thunderbolt is a "fraud" and doesn't care about Patch or his family; he just wanted "his name back in the papers." Lightning then told Thunderbolt that there was never a plan to replace him, saying he just had to get him out of the way. He then announces that he is going to take his place on the show, adding, "My show!". With his plan carried out, the traitorous corgi escapes while laughing evilly, leaving the others locked away.
As soon as the television filming of The Lil' Lightning Show began, Lightning gets caught on the driving window of a double-decker bus ridden by Patch during his escape from Cruella and her henchmen. The bus soon drives into an alley, heading straight for a brick wall. Lightning screams and prepares himself for impact, but fortunately, Patch pulls the brakes. The bus halts inches away from the wall; when Lightning opens his eyes, he passes out, sliding off the window.
During the final battle, Lightning emerges from underneath the bus and watches in shock and horror as Cruella tries to kill Thunderbolt with a crowbar, only to hit Jasper and Horace instead. Thunderbolt performs a dramatic death scene, earning Lightning's sympathy. Thunderbolt bids Lightning farewell and collapses. This makes Lightning burst out in tears, saying, "Good night, sweet prince," ultimately regretting his past actions. However, Thunderbolt drops the act and briefly licks Lightning's face, stunning and confusing him. Patch reverses the bus as he and Thunderbolt watch it roll toward Lightning. He immediately retreats, soon followed by Cruella and her henchmen. The bus sends them running out into the River Thames, ultimately defeating them.
Later, the police arrive and arrest Jasper, Horace, and Lil' Lightning. Lightning tries to convince the police dogs that he was "helping" Thunderbolt as they are a team, to no avail. Lightning is then sent to the pound. His popularity is lost as well, with a newspaper heading in the credits mentioning his arrest and regarding him as "the unkindest cut of all."
- Lil' Lightning's personality and mannerisms are similar to his voice actor Jason Alexander.
- Lil' Lightning is not a true villain as when Thunderbolt faked his death, Lil' Lightning immediately burst into tears, believing him to be dead. He is also not in the least bit evil as he had never intended to kill Patch, Thunderbolt, or anyone.