Whilst playing SLASH'EM (current stable version), I encountered a chameleon in Sokoban's final level that morphed into a leprechaun wizard. That leprechaun wizard cast a spell of invisibility. The chameleon then morphed into a Summon Nasties monster (did not know what it was as I did not have See Invivible nor Telepathy). It remained invisible, and all of the nasties it summoned were invisible. The "E" word worked a few times, failed a couple of times. There was a Green Dragon and some other big and mean nasty. This character perished.
Now, my question or reason for bringing this up is -- is this a bug? The way the invisibility carried over to the new morphed monster? More of a concern is, as to if it is a bug or feature, the summoned invisible creatures? That sounds buggy to me.