Fancy theorem style

Question

I want to write some theorems with the outputs somewhat self-defined like "Theorem A, Theorem B, Theorem B^+, Theorem B^#" etc. and want theses special theorems to be outside of the normal theorem counter, i.e. the other theorems keep their own numbering like "Theorem 1.1, Theorem 1.2" even through "Theorem B" is between them. Is there an easy way to achieve this?

This might be related to the question here but I think that's not pricise my question here. Thanks in advance!

Answer 1

Something like this?

\documentclass{article}
\usepackage{amsthm}

\newtheorem{theorem}{Theorem}[section]
\newtheorem{theoremvar}{Theorem}
\newenvironment{theorem*}[1]
 {\renewcommand{\thetheoremvar}{#1}\theoremvar}
 {\endtheoremvar}

\begin{document}

\section{Title}

\ref{normal1},
\ref{normal2},
\ref{normal3},
\ref{normal4},
\ref{special1},
\ref{special2},
\ref{special3}

\begin{theorem}\label{normal1}
This is a normal theorem.
\end{theorem}

\begin{theorem}\label{normal2}
This is a normal theorem.
\end{theorem}

\begin{theorem*}{A}\label{special1}
This is a special theorem.
\end{theorem*}

\begin{theorem}\label{normal3}
This is a normal theorem.
\end{theorem}

\begin{theorem*}{B$^+$}\label{special2}
This is a special theorem.
\end{theorem*}

\begin{theorem*}{B$^{\sharp}$}\label{special3}
This is a special theorem.
\end{theorem*}

\begin{theorem}\label{normal4}
This is a normal theorem.
\end{theorem}

\end{document}

The theorem* environment has a mandatory argument for the special label.