Gintama': Enchousen

Watch the first episode and you will see why Ixion Saga DT is like Gintama. A lot of the jokes are variations of Gintama jokes. This anime was totally inspired by Gintama. Gintama is so unique that it inevitably was going to inspire a whole new genre of anime. I think Ixion Saga DT is the first of many Gintama-genre anime to come.  

Calling both of these hilarious would be an understatement. Despite a considerable difference in setting, Gintama' Enchousen and SKET Dance share a similar comedic style that could best be summed up with one word - randomness. The very purpose of Yorozuya and Sket-Dan are fundamentally the same: they do anything for their clients. In most cases, both of them go through outrageous lengths in order to accomplish their tasks. Moreover, both groups are composed of three members who play very similar roles: a leader, a strong female, and an otaku. Their personalities are so strikingly similar that a crossover was made highlighting that very premise. The main aspect that distinguishes both series from the rest is its unique sense of humor. Both series parody other anime series but do so in a brilliant and creative manner. If Gintama is considered the king of comedy, Sket Dance would be the prince. read more 

Both gag anime both have similar art style 

Both series feature the same style of comedy. However, each episode of Danshi Koukousei is a collection of short skits, while Gintama is not.