Nicky and Alex Katsopolis were a fun surprise for the later years of Full House. Jesse and Becky got married in season four, and Becky announced her pregnancy shortly after that. Season five brought a chaotic welcome for the little twins, who were born on the day of Michelle's birthday and party.
The Tanners love the youngest additions to the family, but it isn't always easy to take care of two toddlers, especially after raising three girls already. As much as some fans love them, not everything about Nicky and Alex makes sense.
Narrative
Some easy questions arise between the end of Full House and the beginning of Fuller House. Rather than just getting random twins off the street, the reboot cast the original actors, Blake and Dylan Tuomy-Wilhoit. The boys show up as college-aged taco truck hopefuls.
So much information is missing on where they went to school, how they grew up, what their hopes and dreams are, really anything that fans wanted to know.
Absence
While Nicky and Alex were around plenty for Full House, they were on all of two episodes of the spin-off. They rolled up to show how slouchy they were for the first episode, and they came for the Tanner/Fuller Thanksgiving in the first season.
As Stephanie and DJ's cousins, Nicky and Alex should have been featured a few more times. At least they showed up in the first place.
Dialogue
In the Full House/Fuller House family tree, Nicky and Alex are the second significant on-screen babies. The first is obviously Michelle, and the last is DJ's baby, Tommy.
Michelle is the only toddler to say anything exciting. Her baby wrangler trained her well. Nicky and Alex can repeat a few words here and there, but nothing like their cousin, Michelle. As for Tommy Fuller, the poor kid is forgotten almost immediately and maintains a sad level of involvement up to the show's finish. Thank goodness Nicky and Alex actually do things.
Milestones
Everyone is important in the Tanner home, but Nicky and Alex only get to live in it for about three and a half years (that are on film). As a result, they don't get to celebrate as many milestones as Stephanie, Michelle, or DJ. The boys definitely learn to crawl on camera, which Jesse keeps missing.
But other than a few baby/toddler things, the boys aren't the center of attention. There was plenty of interesting stuff to keep up with by the show's last few seasons, but one wonders what else Nicky and Alex might have gotten into.
Bedroom
It is hard to believe that even two babies can fit in that little broom closet in Jesse and Becky's attic apartment. At the beginning of Fuller House, Kimmy's daughter refuses to live in the hobbit-sized space.
Once Nicky and Alex are toddlers, they get race car beds in that room. How those things fit in there is a great mystery.
Ages
Nicky and Alex aren't exactly SORASed. SORAS is "soap opera rapid aging syndrome" and would apply more to characters who go from birth to kindergarten in a couple of episodes, like Jonathan Matthews on Boy Meets World or Chrissy Seaver on Growing Pains.
Nicky and Alex don't make that big of a jump, but they do go change from infants to toddlers rather quickly. Baby Nicky and Alex were played by Daniel and Kevin Renteria until the Tuomy-Wilhoit boys took over for the age-up.
Hair
With the quick jump to the terrible twos (it would seem), the boys grow hair so quickly that their Uncle Jesse is probably questioning it in his mind.
The poor things run around with their bangs in their eyes half the time, but haircuts are quite a source of tension between Becky and Jesse.
Gender Norms
This one isn't the boys' fault, but Uncle Jesse is so set on keeping them away from girl toys. He wants their hair in their faces, but he doesn't want them to play with Michelle's doll or get kisses from Aunt Ida.
Jesse will stop at nothing to make those kids macho men, but Becky talks some sense into him so that the boys actually get a chance to express themselves.
Comparison with Olsen Twins
Some may be inclined to constantly compare Nicky and Alex to the Olsen twins who played Michelle.
While this is natural, it doesn't totally make sense. Michelle has a much longer run on the show than her little cousins, and while she is played by twins, she, herself, is not a twin.
Order of Names
With that said, Jesse's boys take after the Olsens in a very distinct way. Rarely do fans say "Ashley and Mary-Kate Olsen." Just as it's always "Mary-Kate and Ashley," it's always "Nicky and Alex."
It seems like Alex will just never come first; he's relegated to the second banana in his twindom. This situation is not uncommon for real twins, but it would be considerate to switch the names up from time to time.