Hm... how about Holly? Or if someone already suggested her, Mateo?
for holly, i chose mostly pokemon that i could associate with the various holidays that she's representing, so i went with:
delibird (for christmas, obviously)
luvdisc (for valentine's day)
pikachu (here's the outlier, as in pikachu isn't holiday-themed, but holly is just SO booked and busy all the time, and that's absolutely true for Franchise Mascot pikachu as well. also, their respective energies match really well, imo!)
buneary (for easter; shiny, because the pink matches the holiday the best, and holly absolutely would have a shiny pokemon somewhere on her team)
duskull (for halloween; it was between this or pumpkaboo, but holly's skelly decoration on her design decided this one! plus, as it evolves, it'll get spookier and spookier! perfect for the holiday!)
pansage (the closest i could find to a pokemon that'd work for st. patrick's day! the tail isn't exactly a clover, and pansage isn't exactly a leprechaun, but its pokedex entries mention it being able to share with friends and relieve stress, which is a good start to any st. paddy's day celebration to me! plus, holly could use a pokemon that'll help her mellow out when she needs to)
for mateo, i opted to lean into his relaxed, cuddly vibes, as well as his drive to make the lost and unwelcome find a home:
stoutland (obligatory dog for his team, with a history of rescuing stranded people and keeping them warm and cozy with its fur. a no brainer for mateo!)
audino (a kindhearted caretaker type, with the ability to tell how someone's feeling based off of their heartbeats. another warm, cuddly type who would help rescues feel safe and cared for)
wooloo (fluffy and soft, with wool that can make many strong blankets, according to the pokedex entries! just picture yourself cuddling a wooloo. that's what mateo would want for everyone)
pachirisu (an often overlooked member of the electric rodent trend, imo. i think he'd have one because so many people don't! and mateo's likes are listed as "snuggles, cuddles, nuzzles" in-game, and what electric move does this little guy know? call it a blanket-induced static shock!)
wigglytuff (back at it again with the normal types! this one's got more than one pokedex entry about snuggling and being difficult to pull away from a snuggle partner, and that's just a great vibe. a lot of its pokedex entries mention it being very soft and nap-on-able as well, but since it'll also expand itself when threatened, i think it strikes a great balance between mateo's drive to comfort and protect the underdogs out there)
bruxish (listen. it's often the number one least liked pokemon on like. so many lists. people say such mean things about bruxish, and you just know that'd break mateo's heart. you know it. he'd make sure at least one would feel wanted!)