"Matchbox" is a song written and performed by legendary Rockabilly performer Carl Perkins, that was also recorded by The Beatles. The song has a long history, parts of its lyrics were orginally written by Blind Lemon Jefferson in the 1920s. The Blind Lemon Jefferson version was a travelling song, with him wondering "will a matchbox hold my clothes?". The Perkins version, performed by the Beatles, combines that with some very obvious innuendo, asking:

Can I be your little dog, momma, til your big dog comes? When your big dog gets here, show him what this little puppy done
Which seems to suggest that it is okay to have an affair, as long as the man has a small penis(?) and you also show what exactly happened. I don't know exactly, they had to be vague and slurry about their innuendo back in the 1950s, even when it was obvious.

The interesting thing to me is how the song combines different folk motiffs in two minutes. The matchbox is doubly a symbol of the poverty of the travelling musician, but also seems to tie in with the idea of him being a folklorishly small figure, a Paul Bunyan in reverse. The song also suggests that the singer is an impoverished loser, with Perkins singing that "everything I do is wrong", but is also a roving seducer, despite advertising his lack of... "assets". The song complains and swaggers and rocks all at the same time.

The song's recording history with the Beatles was also a bit odd, since it never occurred on one of their "core albums", instead appearing on the Long Tall Sally EP, and later on the non-core "Something New" album.