It's not uncommon for Pokemon games to freshen up old evolutionary lines with brand-new evolutions, and this is once again the case in Pokemon Scarlet & Violet. The games don't feature quite as many cross-generation evolutions as some of their predecessors, but there are still several interesting additions to the Pokedex nonetheless, with Pokemon from several past generations benefiting from powerful new forms.
Pokemon Scarlet & Violet: Every New Cross-Gen Evolution (& How to Get Them)
There aren't too many cross-generation evolutions in Pokemon Scarlet & Violet, making it relatively easy for players to add them all to their Pokedex.