LaTeX Beamer: Enumerate with manual numbers

Question

I'd like to do the following enumeration in beamer;

1. First Item
2. Second Item
3. Third Item
3'. Alternative Version of Third Item.

However, if I do this:

  \begin{enumerate}
    \item First Item
    \item Second Item
    \item Third Item
    \item[3'] Alternative Third Item
  \end{enumerate}

then the last item doesn't appear with the usual bullet style.

Help? Thanks!

Answer 1

The following solution is independent of the theme used and will always produced the appropriate format for the items in the first level of enumerate (the minipages in the example are just for brevity and are not relevant for the solution):

\documentclass{beamer}
\usetheme{Warsaw}
\usepackage{etoolbox}

\newcommand\Pitem{%
  \addtocounter{enumi}{-1}%
  \renewcommand\theenumi{\arabic{enumi}'}%
  \item%
  \renewcommand\theenumi{\arabic{enumi}}%
}

\begin{document}

\begin{frame}
\begin{minipage}{.5\linewidth}
\begin{enumerate}
\item First.
\item Second.
\item Third.
\Pitem Third prime.
\item Fourth.
\item Fifth.
\item Sixth.
\Pitem Sixth prime.
\item Seventh.
\end{enumerate}
\end{minipage}%
\begin{minipage}{.5\linewidth}
\setbeamertemplate{enumerate item}[square]
\begin{enumerate}
\item First.
\Pitem First prime.
\item Second.
\item Third.
\item Fourth.
\Pitem Fourth prime.
\item Fifth.
\item Sixth.
\item Seventh.
\end{enumerate}
\end{minipage}%
\end{frame}

\end{document}

Use \Pitem for the item(s) that will be "primed".

Answer 2

If you want to use the same style for the bullet, but would like to change its label, you can use the following

\documentclass{beamer}
\usetheme{Warsaw}
\newcommand{\labelname}[1]{
    \def\insertenumlabel{#1}%
    \usebeamertemplate{enumerate item}%
}
\begin{document}
\begin{frame}
    \begin{enumerate}
        \item first
        \item[\labelname{1'}] prime
        \item second
    \end{enumerate}
\end{frame}
\end{document}

The above code results in

Answer 3

I copied the bullet format, but I just faked the itemize format.

\documentclass{beamer}
\usetheme{Warsaw}

\newcommand{\myitem}[1]% #1 = text inside bullet
{
  \par\vspace{3pt}\hspace*{-15pt}%
  \begin{pgfpicture}{-1ex}{-0.65ex}{1ex}{1ex}
    \usebeamercolor[fg]{item projected}
    {\pgftransformscale{1.75}\pgftext{\normalsize\pgfuseshading{bigsphere}}}
    {\pgftransformshift{\pgfpoint{0pt}{0.5pt}}
      \pgftext{\usebeamerfont*{item projected}#1}}
  \end{pgfpicture}%
  \hspace{1pt}%
}

\begin{document}

\begin{frame}
\begin{enumerate}
  \item first
  \myitem{1'} alternate
  \item second
\end{enumerate}
\end{frame}

\end{document}