This study is targeted towards the explosive behavior of crypto-currencies, namely Bitcoin, Etherium, Litecoin and Ripple by investigating the crypto-currencies bubbles and the causal link between Bitcoin and other three crypto-currencies prices, using GSADF and wavelet coherence tests. The study aims to answer the following questions which have not been investigated in the literature to our best knowledge (i) Was there any bubble in the prices of Bitcoin, Etherium, Litecoin and Ripple and between 01.09.2016 and 01.04.2019? If yes, why (ii) was there any linkage between Bitcoin and Etherium, Litecoin and Ripple? Our findings reveal that (a) there were some bubbles in the crypto-currencies for the periods investigated; (b) there was a positive correlation between Bitcoin and Etherium, Litecoin and Ripple in the short-run; (c) changes in Bitcoin prices lead changes Etherium, Litecoin and Ripple prices in the long run at different periods.