Anal on my boyfriend

So my boyfriend asked me if I'd like to do anal on him.. I didn't know how to respond, so I kinda shook it off and said, If i can take it, you can take it (jokingly of course)but he was serious, As we brought it up again. He really wants me to buy a strap on and "I get to have my way with him"... I dont think it's strange much, it was just out of the blue... I just keep asking him if he's sure about it... And I don't quite know how to reaspond or what our next step would be.