Better we divert than our flights!
But before we refuel and get back to ordinary route, I just realised where 'hoppeligen' comes from.

Adding "-en" to adjectives is a very rare style of making adverbs out of adjectives. (the normal way is to add "-t") I don't think it has been used for a really long time, but it lives on in a few common words, especially in adjectives ending in "-lig" that are used in adverbials:
Trolig - Troligen (Probable - Probably)
Verklig - Verkligen (Real - Really)
Tydlig - Tydligen (Clear - Clearly)
Möjlig - Möjligen (Possible - Possibly)

(they all have "-t" form aswell, troligt/verkligt/tydligt/möjligt but are then plain adverbs, not used in adverbials)

I can't recall any adjectives not ending in "-lig" officially having this form, but there are some used in a pretentious way (in adverbials) and what they do is that they fake being "-lig" adjectives before adding "-en" !
Knapp - "Knappeligen" (Scanty - Scantily)
Säker - "Säkerligen" (Sure - Surely)

So 'hoppeligen' just followed a pattern (with the odd twist of starting with a noun instead of an adjective) and fits logically into the language.