Portulaca grandiflora (Moss Rose)

Photo #2 is a Kalanchoe daigremontiana - it propagates prolifically from tiny plantlets growing alongside the leaf edges (you could see couple of babies on one of the leaves). In some areas, they could become weedy :)

The smaller plant looks like it may be Alworthia 'Black Gem'. The taller one may be a severely etiolated Echeveria - hard to tell for sure since it's stretched so much looking for more light. Whatever it is, it should be in a tight rosette - much less space between leaves - and much closer to the soil.

You're so right! I feel like a dummy about the Frosty, because I see its crested form all over the place...guess I'd just never seen the normal kind before. But that's totally it. I'm almost positive you're correct about the cactus, too. Thanks for your help!