But where do you personally draw the analytical line? The Wolf 359 ships and the Frankenstein fleet were meant to be regular 23rd or 24th century designs, and they would've been if the needed budget was there along with the requirement to show them up-close. To what extent do you think they look like the models on the available photos? NCC-42 is an injoke, yes, but in a way so is the highly visible NCC-1941 from "Cause and Effect" (TNG), not to mention NCC-0514 for the likewise visible Kelvin
and a few other numbers from the background STXI ships. The Elmer Fudd
is extremely unlikely because that name is highly inconsistent with Starfleet nomenclature, but NCC-42... Depends. Maybe it's an old ship that has seen some upgrades and is restricted to very specific missions.