You can finally rescue Half-Life's guards and scientists thanks to this mod inspired by Lemmings
(www.pcgamer.com)
Half-Life: Lemmings lets you save the trapped employees of the Black Mesa: Facility.
Trailer:
It's important to note that the mod is built for Half-Life: Source rather than the original version.
I assume this was to allow for the more advanced NPC behaviours, but targeting a delisted and near-universally panned remake is certainly a choice.