It's a competition for Kate on the episode "Overkill." As this promo teases, Demming and Castle must work together, which means each trying to earn Beckett's attention.
Beckett:I cannot believe you asked for samples. Castle:What they said anything we want plus these aren't for me they are for Ryan and Esposito. Beckett:Don't you mean Charlotte and Miranda. Castle:Wait that would make me Carrie. Beckett:You are so metrosexual for even knowing that. Castle:Hey only watched that show out of the corner of my eye when my mom had it on.... that didn't make my point quite like i wanted it to.