It is one of the fundamental problems to understand how and what kind of hadron spectrum emerges from quantum chromodynamics (QCD), the theory of the strong interaction. Tremendous progress has been made since 2003 due to the discoveries of many unexpected resonances. Here I will talk about the effects of singularities caused by special kinematics, and in particular the so-called triangle singularities, in resonance searching. On the one hand, they can mimic resonances. On the other hand, once a resonance has been established, the singularities may be used to find processes with enhanced production rates. As examples, I will discuss the cases of the tetraquark candidate Zc(3900), pentaquark candidate Pc(4450) and the search of a hypothetical Ps.