why cyclobutyl methyl carbocation cannot show dancing resonance?
CH2+ has a vacant p-orbital and a very effective overlapping takes place between p-orbital and electron density of cyclopropane ,as shown if figure,and due to this its stability is very high. There is a conjugation between the sigma bond(lone pair) and +ve charge.
Dancing resonance is a hypothetical phenomenon which is shown in structures of carbocations attached directly to a 3 membered ring.