Fergonzo is the romantic ship of Alfonzo Dolittle and Ferguson O'durguson.
Alfonzo and Ferguson have very rarely been seen without the other, and when one is missing or in danger, the other always expresses extreme concern over the fact, even if nobody else does. Whenever Ferguson is in danger (such as in "Mewnipendence Day", when the super-sized mace fell on him), Alfonzo is the first to act; additionally, when separated, the first thing they do when reunited is immediately cling to the other, as seen in "Pixtopia."
In "Interdimensional Field Trip," before going through the portal that merged them into a 'friendtaur', they held hands and went in together, before reacting ecstatically at them being two people with one body. Afterwards, once separated, they repeatedly ask Star to put them back together again, as shown in "Star and Marco's Guide to Mastering Every Dimension."