In this talk, I will introduce recent developments about the integrable scalar peakon/ pseudo-peakons models, including the well-known Camassa-Holm (CH), the Degasperis-Procesi (DP), and other new peakon equations studied in recent years. These models are in general produced from the negative order flows of the integrable hierarchy. In particular, the CH model is extended to the DP, the b-family, the FORQ, the Novikov, the modified CH (MOCH), and other higher order differential models we developed recently with peakons, pseudo-peakons, and weak-kink solutions. Multi-pseudo-peakon system is constructed and proved integrable (more details, please see arXiv:2111.07733). open problems are addressed in the end. Some work is joint with Guoping Zhang, Baoqiang Xia, Mingxuan Zhu, and Enrique Reyes.