Unlike Les Pyjamasques, the PJ Masks are more of a trio of DC Comics-esque superheroes going on missions to fight real crime, instead of being a trio of adventure-type superheroes.
Another difference between the groups is that the PJ Masks are not interested on playing in the night than Les Pyjamasques, and prefer to jump straight into saving the day while patrolling the streets for villains in the similar fashion to common vigilante superheroes.
Rather than sticking on Les Pyjamasques' goals to go on adventures and stopping villains from altering the normality of the night and/or preventing a villain's revenge plan (to redeem their negative lives), the PJ Masks tend to go on typical superhero missions to prevent any villains from doing anything that's bratty which can create trouble throughout their city (in the day).
Most of their missions include:
Stopping a villain from destroying or invading their HQ modeled after Les Pyjamasques' totem for a villain's selfish and superior purposes.
Stopping a villain from becoming the most powerful person in the world.
Preventing building break-ins of villains such as the museum and Mystery Mountain's pagoda who needs a key artifact that looks handy to use in his/her plan.
Preventing any generic theft and misuse of possessions and objects, even acting somewhat strict if a villain is using them without meaning any harm nor ruining things for everyone else (as emphasized in "Owl Eyes" and "Moonbreaker").
Unlike Les Pyjamasques, the PJ Masks would also need to choose a vehicle to get to the location in which the fight between the villain and hero takes place rather than going on foot, as they are not used to travelling to locations without a vehicle and not as athletic as Les Pyjamasques (as emphasized in "Romeocoaster").
In shorts, more details on the PJ Masks roles are revealed such as shipping and packing crates to HQ from the Moon in "Moon Cuddly", exploring Mystery Mountain in "PJ Rovers", practicing their hero moves in "Owl Eyes". And occassionally, their general roles are downplayed in some of their appearances such as playing in the night in the similar fashion to Les Pyjamasques in "PJ Racing".
In each of their appearances, the PJ Masks in the day or night (in some cases) are often disrupted while playing each other or in a conversation whenever they see some recent leftovers of villain activity and decide to investigate it.
Then during in bedtime (and nowhere near midnight), the PJ Masks activate their PJ Masks Bracelets that link to their super-powered pajamas to change them to costumes and teleport to HQ.
After they transform, the PJ Masks would look at the PJ Picture Player for clues for villains, then they choose a vehicle, however, unlike Les Pyjamasques, they cannot say "X, come to us!" to summon the vehicle they chosen, instead one of the PJ Masks will proclaim their choice of the vehicle by saying "To the X!" while going to the chosen vehicle.
Midway through their location on where the fight between the villain would take place, Catboy or Owlette would either use their sensing abilities to track the villain responsible for the destruction. As they succeed, they will head over to the location where they would confront the villain.
Once they reached the location, they would confront the villain through the steps of Prosecution. However, unlike Les Pyjamasques, the leader of the PJ Masks will form a step-by-step strategy plan to stop the villain's mission. Once the villain is defeated and fled from the heroes, the PJ Masks will proclaim their victory.
The PJ Masks consist of:
Catboy (Connor): A cat-like kid with super-speed and great hearing abilities. He is the leader of the trio and drives the Cat Car. His suit is dark blue in color and has ears and a tail.
Owlette (Amaya): An owl-like girl with flying abilities and a special ability to see things from far away using her owl eyes. She is the only female member of the group and flies the Owl-Glider. Her suit is red and has an owl mask with feathered wings on her back.
Gekko (Greg): A lizard-like boy with super-strength, the ability to climb walls and ceilings, and the ability to color-change and camouflage. He is the youngest of the trio and drives the Gekko-mobile. His suit is green in color and has reptilian features.
PJ Robot: A robot with the ability to hover above the ground. He maintains HQ, acts as mission control for the team, and occasionally accompanies the heroes on missions.
Unlike Les Pyjamasques, the PJ Masks tend to act like adolescents between preteen and teenager age (and occasionally like adults) rather than behaving like average kids, and having a mature and polite personality that is reminiscent to Lilifée's behavior. In occasions, they will act childlike like their book counterparts, though, they will often resist from doing so to prevent on losing focus during missions.
In missions, the members of the trio had moments of outdoing each other and failing to cooperate, which resulted the villains getting the better of them until they realize the mistakes they made.
Unlike Les Pyjamasques, it is unknown when and how the PJ Masks got formed, but it is confirmed in "HQ Tour" that their adventures on saving the day started in "Blame it on the Train, Owlette", though it might've been way earlier than that.
The PJ Masks are not the only ones whose formation is unknown, as Les Pyjamasques' original counterparts are alongside them too.
In "PJ Dylan", it was thought that Armadylan was an actual member of the trio, but this was resolved at the end of the episode when the PJ Masks decided that he can help them once at a while (but not as a member).
It is unknown if the PJ Masks have had any members other than the current trio.
Their catchphrases, usually said by either Connor, Greg, or Amaya, is "PJ Masks, we're on our way. Into the night, to save the day!" or "Pyjamasques, on a un nouveau défi, les soucis, on les règle la nuit!" (in the French dub).
It is possible that when they switch at nighttime, they start thinking more like animals. They are able to trot on all four legs like an animal would, have catchphrases (and insults thrown at them) that relate to the animal they're based off of, and are able to get into poses that the animal they're based off of would be able to.
The only PJ Masks shown in the current trio that does not have a tail is Owlette and PJ Robot and this can be seen if one looks at their poses thoroughly.
According to a YouTube video from the official PJ Masks channel, the PJ Masks are all 6 years old (the description reads "Six year olds Connor, Amaya, and Greg", thus confirming Les Pyjamasques' age). The villains' ages are currently unknown, but they could be around that age as well.
Whenever their powers are activated their costumes will glow a lighter color of their signature colors. They also usually call out the names of their powers upon activating them, but not always.
Other characters who have that similarity is Yoyo (although, his costume would no longer have the glowing feature in his later appearances).
Unlike the rest of Les Pyjamasques' counterparts playful acrobatic routine when off-duty, the PJ Masks will instead take their time off-duty such as practicing their hero moves near HQ or taking their vehicles for a ride.
The PJ Masks would choose to act casual, discreet and blend in from the public such as hiding or disguising their voices so that no one will know who they really are.
The PJ Masks' group name and member names were eventually adopted as nicknames for Les Pyjamasques by fans outside France, despite the PJ Masks and Les Pyjamasques being considered separate characters and group by continuity.
Some of the fans ignored the fact that PJ Robot is the "fourth PJ Mask to the team", and refer a new character they suggested to be added to the TV series as a "fourth PJ Mask" member.