Are those blooms on the ends? That would make me think of Astrophytum caput-medusae. Good grief, are they so common that they are handed out as favors? Great gift if it turns out to be A. c-p.! If the stems are brownish and they feel sticky because of the spines, then it puts me thinking of a South American Opuntioid. The arms fall off easily and grow roots quickly, and the root puts up more arms. Can't think of the name. If nobody comes along with an ID, a neater photo and a few more words of description could help.

Sorry, but I don't know or grow this plant (did so only very briefly), so I'll defer to other on this & Fred's suggestion sounds like a good start. But a caution, if you don't know, when you do cut it back (or for accidental breakage), best wear gloves or be extra careful to wash up & not touch your face 'til you do. If this is Euphorbia tirucalli, the white sap it exudes when cut can be a skin irritant. If its size is becoming an issue, there's no law that says you MUST repot it larger; you could keep it in the same size pot, & perhaps control its size SOMEWHAT by doing so.

IF you have root rot on your upright pencil cactus, you can take BIG cuttings from it, let them dry for a few days, and pot them into a very fast draining cactus soil, and let it re-root. From the picture, it looks like the upright one is still growing, Or let the soil dry out totally, or as much as you can, no water at all till it is dry way down. That MAY stop the rot, if you have root rot. BUT is it getting ANY full direct sun on it?? It needs as much direct full sun all day as you can give it, or it will become weak and topple as it grows. I dont know what that second crawling cactus is. Is it suppose to crawl? I grow the red variety of the pencil cactus here in Fla. To get it to turn and stay red, it needs full direct sun all day. it is the 'Sticks on Fire' variety. It is in full direct sun outside all day. The green one also needs as much sun as possible, to grow sturdy and rather fast! . But it survives with less light, but just not as strong as if it was in desert conditions. I dont know where you live ,but if you can move the plants into more direct sun, and stake up the tall one, it will get stronger and stand up on its own,with minor pruning.

I would give it a good soaking,and if it doesn't perk up, check the roots. Either way, repot into a better well-draining soil mix with NO SAND. Use half soil, half perlite. A smaller pot would also help. And I hope you know about the toxic latex this plant produces, be careful handling it. .. good luck