The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
That'd be a good example of Continuity Creep - it can take different forms, one of them being a gradual creep of worldbuilding without necessarily developing more elaborate storylines.
Also, Early-Installment Weirdness isn't limited to elements that become obsolete: It can also involve things like early installments missing some element that becomes a defining feature of the series. For example, JoJo's Bizarre Adventure didn't introduce the iconic Stands until Part 3. Even then, the first batch were named/themed after tarot cards rather than music shout-outs, and tended to be more straightforward combat powers than the powers of later Stands that revel in Heart Is an Awesome Power and Lethal Harmless Powers.
Edited by Scorpion451
^ Sure, it can be shoehorned into Continuity Creep, but the latter's current definition focuses entirely on narrative threads, rather than rules and limitations of the setting, so I was wondering about a separate entry.
Do we have a trope for when a serialized story starts off with relatively soft Worldbuilding (i.e. the author doesn't hesitate to throw random stuff in for the sake of narrative or just a laugh), which eventually gets harder and harder in the sequels, as the rules of the setting become formalized and ossified? So far, I have found Continuity Creep (which is related, but not the same) and Early-Installment Weirdness (which is only for elements that become obsolete as the world rules get nailed down).